![Starting a Java Program (Sample)
import java.lang.System;
import java.lang.String; or use import java. lang.*;
class First
{
public static void main (String args [])
{
System.out.println (“Welcome to Java”);
}
}](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-34-320.jpg)
![public class IntDemo{
public static void main(String args[]){
System.out.println(" For an Integer ");
System.out.println("Size is : "+Integer.SIZE);
int i1 = Integer.MAX_VALUE;
int i2 = Integer.MIN_VALUE ;
System.out.println("Max value is : "+i1);
System.out.println("Min Value is : "+i2);
System.out.println(" For an Byte");
System.out.println("Size is : "+Byte.SIZE);
byte b1 = Byte.MAX_VALUE;
byte b2 = Byte.MIN_VALUE ;
System.out.println("Max value is : "+b1);
System.out.println("Min Value is : "+b2);
System.out.println(" For an Short");
System.out.println("Size is : "+Short.SIZE);
short s1 = Short.MAX_VALUE;
short s2 = Short.MIN_VALUE ;
System.out.println("Max value is : "+s1);
System.out.println("Min Value is : "+s2);
System.out.println(" For a Long");
System.out.println("Size is : "+Long.SIZE);
long l1 = Long.MAX_VALUE;
long l2 = Long.MIN_VALUE ;
System.out.println("Max value is : "+l1);
System.out.println("Min Value is : "+l2);
}
}](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-49-320.jpg)
![public class FloatDemo{
public static void main(String args[]){
System.out.println(" For an Float");
System.out.println("Size is : "+Float.SIZE);
float f1 = Float.MAX_VALUE;
float f2 = Float.MIN_VALUE ;
System.out.println("Max value is : "+f1);
System.out.println("Min Value is : "+f2);
System.out.println(" For an Double");
System.out.println("Size is : "+Double.SIZE);
double d1 = Double.MAX_VALUE;
double d2 = Double.MIN_VALUE ;
System.out.println("Max value is : "+d1);
System.out.println("Min Value is : "+d2);
}
}](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-50-320.jpg)
![public class CharDemo{
public static void main(String args[]){
System.out.println(" For a Char");
System.out.println("Size is : "+Character.SIZE);
int f1 = Character.MAX_VALUE;
long f2 = Character.MIN_VALUE ;
System.out.println("Max value is : "+f1);
System.out.println("Min Value is : "+f2);
}
}](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-51-320.jpg)
![Variables
The variable is the basic unit of storage in a Java program.
A variable is defined by the combination of an identifier, a type, and an
optional initializer.
Declaring a Variable
In Java, all variables must be declared before they can be used.
type identifier [ = value][, identifier [= value] ...] ;
Types
Instance Variable
Class Variable
Local Variable
Parameters](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-52-320.jpg)
![class Variables{
int i;
public int j
static long l=10;
public static float f;
char c;
boolean b;
void display(int a){
i=a;
System.out.println("i value in display: "+i);
}
public static void main(String args[]){
double d=0.0;
//public double d=0.0; invalid
Variables v1=new Variables();
Variables v2=new Variables();
Variables v3=new Variables();
v1.display(100);
v1.i=2;
v2.i=3;
v3.i=4;
System.out.println("i value is: "+v1.i);
System.out.println("i value is: "+v2.i);
System.out.println("i value is: "+v3.i);
System.out.println("i value is: "+v1.j);
v1.l=20;
v2.l=30;
v3.l=40;
System.out.println("l value is: "+v1.l);
System.out.println("l value is: "+v2.l);
System.out.println("l value is: "+v3.l);
System.out.println("f value is: "+f);
System.out.println("c value is: "+v1.c);
System.out.println("b value is: "+v1.b);
System.out.println("d value is: "+d);
}
}](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-56-320.jpg)
![class Variables{
int i;//instance variable
public int j ;//instance variable
static long l=10;//class variable
public static float f;//class variable
char c;//instance variable
boolean b;//instance variable
void display(int a){
i=a;
System.out.println("i value in display: "+i);
}
public static void main(String args[]){
double d=0.0;//local varible
//public double d=0.0; invalid
Variables v1=new Variables();
Variables v2=new Variables();
Variables v3=new Variables();
v1.display(100);
v1.i=2;
v2.i=3;
v3.i=4;
System.out.println("i value is: "+v1.i);
System.out.println("i value is: "+v2.i);
System.out.println("i value is: "+v3.i);
System.out.println("i value is: "+v1.j);
v1.l=20;
v2.l=30;
v3.l=40;
System.out.println("l value is: "+v1.l);
System.out.println("l value is: "+v2.l);
System.out.println("l value is: "+v3.l);
System.out.println("f value is: "+f);
System.out.println("c value is: "+v1.c);
System.out.println("b value is: "+v1.b);
System.out.println("d value is: "+d);
}
}](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-57-320.jpg)
![& //executes both left and right side operands
&& // Java will not bother to evaluate the right-hand
operand when the outcome of the expression can be
determined by the left operand alone.
class Test{
public static void main(String args[]){
int denom=0,num=20;
if (denom != 0 && num / denom > 10)
System.out.println("Hi");
}
}](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-63-320.jpg)
![Example:
class IncDec{
public static void main(String args[]){
int a = 1;
int b = 2;
int c,d;
c = ++b;
d = a++;
c++;
System.out.println("a = " + a);
System.out.println("b = " + b);
System.out.println("c = " + c);
System.out.println("d = " + d);
}
}](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-67-320.jpg)
![class OpEquals{
public static void main(String args[]){
int a = 1;
int b = 2;
int c = 3;
a += 5;
b *= 4;
c += a * b;
c %= 6;
System.out.println("a = " + a);
System.out.println("b = " + b);
System.out.println("c = " + c);
}
}](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-68-320.jpg)
![Example:
public class RelationalOperatorsDemo
{
public static void main(String args[])
{
int x=10,y=5;
System.out.println(“x>y:”+(x>y));
System.out.println(“x<y:”+(x<y));
System.out.println(“x>=y:”+(x>=y));
System.out.println(“x<=y:”+(x<=y));
System.out.println(“x==y:”+(x==y));
System.out.println(“x!=y:”+(x!=y));
}
}](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-72-320.jpg)
![public class TernaryOperatorDemo
{
public static void main(String args[])
{
int x=10,y=12;
int z;
z= x > y ? x : y;
System.out.println(“Z=“+z);
}](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-74-320.jpg)
![public class TernaryOperatorDemo
{
public static void main(String args[ ])
{
int x=10,y=12;
int z;
z= x > y ? x : y;
System.out.println(“Z=“+z);
}](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-77-320.jpg)
![Example for for-each
class demo
{
public static void main(String args[])
{
}
}
}](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-85-320.jpg)
![Example for continue
class continuedemo
{
public static void main(String args[])
{
;
}
}
}](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-88-320.jpg)
![Arrays
An array is a group of homogeneous (same type of) elements
that are referred by a common name.
In java, Arrays are created on dynamic memory by JVM.
The operator new is used for dynamic memory allocation.
One-Dimensional Arrays:
Syntax: type variablename[] = {elements list};
ex: int marks[] = {60,70,80,50};
Syntax : type varname[]=new type[size];
int month[] = new int[12];](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-95-320.jpg)
![Multidimensional Arrays
int twoD[][]=new int[4][5];](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-96-320.jpg)
![ If month is a reference to an array, month.length will gives
the length of the array.
Initialization:
char []c = {‘a’, ‘b’, ‘c’};
double d[][]= {
{1.0,2.0,3.0},
{4.0,5.0,6.0},
{7.0,8.0,9.0}
};](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-97-320.jpg)
![Jagged Arrays
X[0] [0] x[0] [1]
X[1] [0] x[1] [1] x[1] [2]](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-100-320.jpg)
![Command Line Arguments
Values passed by the user at runtime from command
prompt are command line arguments.
Represent values passed to main method.
To store these values main has a parameter, String args[ ]
For ex: c:java prog 22 33 anil
These three values automatically stored in main() method’s
args[ ] in the form of strings.](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-102-320.jpg)
![package packagename;
import statement;
class classname{
//instance variables;
//class or static variables;
/*methods(parameters){
//local variables;
//object creation
//statements;
}*/
}
import java.util.Scanner;
class Demon{
int i;
static double d;
public static void main(String args[]){
char c=‘a’;
Demon obj=new Demon();
Scanner s=new Scanner(System.in);
d=s.nextDouble();
System.out.println(obj.i);
System.out.println(d);
System.out.println(c);
}
}](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-110-320.jpg)
![class classname{
//instance variables;
//class or static variables;
/*methods(parameters){
//local variables;
//statements;
}*/
}
class MainCLass{
public static void main(String args[])
{
//object creation
//invoking methods
//statements
}
}
class Test{
char c='a';
static float f;
void display(){
int i=10;
System.out.println("Test:display()");
System.out.println(“c value: “+c);
System.out.println(“i value: “+i);
System.out.println(“f value: “+f);
}
}
class Demo{
public static void main(String args[]){
Test t=new Test();
t.display();
System.out.println("Demo:main()");
}
}](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-111-320.jpg)
![class AccessTest {
public static void main(String args[]) {
Test ob = new Test();
// These are OK, a and b may be accessed directly
ob.a = 10;
ob.b = 20;
// This is not OK and will cause an error
//ob.c = 100; // Error!
// You must access c through its methods
ob.setc(100); // OK
System.out.println(ob.a + " " +ob.b + " " + ob.getc());
}
}
//Example for access control](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-114-320.jpg)
![class Test{
char c='a';
static float f;
Test(){
int i=10;
System.out.println("Test:Test()");
System.out.println(“c value: “+c);
System.out.println(“i value: “+i);
System.out.println(“f value: “+f);
}
}
class ConDemo{
public static void main(String args[]){
Test t=new Test();
//t.Test();
System.out.println(“ConDemo:main()");
}
}
class Test{
int x,y;
Test(int a, int b){
x=a;
y=b;
System.out.println(“x value: “+x);
System.out.println(“y value: “+y);
}
}
class PConDemo{
public static void main(String args[]){
Test t=new Test(10,20);
System.out.println(“PConDemo:main()");
}
}
//Parameterized Constructor// Default Constructor](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-118-320.jpg)
![Program to test which block executes first
class test
{
static {
System.out.println(“From static block”);
}
public static void main(String args[ ])
{
System.out.println(“From static method”);
}
}](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-125-320.jpg)
![class Box{
double width;
double height;
double depth;
Box(){
width=10;
height=10;
depth=10;
}
double volume(){
return width*height*depth;
}
}
class BoxDemo6{
public static void main(String args[]){
Box mybox1=new Box();
Box mybox2=new Box();
double vol;
vol=mybox1.volume();
System.out.println("Volume is: "+vol);
vol=mybox2.volume();
System.out.println("Volume is: "+vol);
}
}
Non parameterized or default Constructor](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-126-320.jpg)
![class Box{
double width;
double height;
double depth;
Box(double w,double h,double d){
width=w;
height=h;
depth=d;
}
double volume(){
return width*height*depth;
}
}
class BoxDemo7{
public static void main(String args[]){
Box mybox1=new Box(10,20,15);
Box mybox2=new Box(3,6,9);
double vol;
vol=mybox1.volume();
System.out.println("Volume is: "+vol);
vol=mybox2.volume();
System.out.println("Volume is:
"+vol);
}
}
Parameterized Constructor](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-127-320.jpg)
![class OverloadDemo {
void test() {
System.out.println("No parameters");
}
void test(int a) {
System.out.println("a: " + a);
}
void test(int a, int b) {
System.out.println("a and b: " + a + " " + b);
}
double test(double a) {
System.out.println("double a: " + a);
return a*a;
}
}
class Overload {
public static void main(String args[]) {
OverloadDemo ob = new OverloadDemo();
double result;
ob.test();
ob.test(10);
ob.test(10, 20);
result = ob.test(123.25);
System.out.println("Result of ob.test(123.25): " + result);
} }
//method overloading](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-129-320.jpg)
![//Constructor Overloading
class CDemo{
int value1;
int value2;
CDemo(){
value1 = 10;
value2 = 20;
System.out.println("Inside 1st
Constructor");
}
CDemo(int a){
value1 = a;
System.out.println("Inside 2nd Constructor");
}
CDemo(int a,int b){
value1 = a;
value2 = b;
System.out.println("Inside 3rd Constructor");
}
public void display(){
System.out.println("Value1 === "+value1);
System.out.println("Value2 === "+value2);
}
public static void main(String args[]){
CDemo d1 = new CDemo();
CDemo d2 = new CDemo(30);
CDemo d3 = new CDemo(30,40);
d1.display();
d2.display();
d3.display();
}
}](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-130-320.jpg)
![// instance and formal variables are different
class Box{
double w=5,h=5,d=5;
Box(double w1,double h1,double d1){
w=w1;
h=h1;
d=d1;
}
double volume(){
return w*h*d;
}
}
class BoxTest1{
public static void main(String args[]){
Box b=new Box(1,2,3);
System.out.println("Volume is: "+b.volume());
}
}
Output:
Volume is:6.0](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-132-320.jpg)
![// instance and formal variables are same
class Box{
double w=5,h=5,d=5;
Box(double w,double h,double d){
w=w;
h=h;
d=d;
}
double volume(){
return w*h*d;
}
}
class BoxTest2{
public static void main(String args[]){
Box b=new Box(1,2,3);
System.out.println("Volume is: "+b.volume());
}
}
Output:
Volume is:125.0](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-133-320.jpg)
![//’this’ hides the instance variables
class Box{
double w=5,h=5,d=5;
Box(double w,double h,double d){
}
double volume(){
return w*h*d;
}
}
class BoxTest2{
public static void main(String args[]){
Box b=new Box(1,2,3);
System.out.println("Volume is:
"+b.volume());
}
}](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-134-320.jpg)
![// Simple types are passed by value.
class Test {
void meth(int i, int j) {
i *= 2;
j /= 2;
}
}
class CallByValue {
public static void main(String args[]) {
Test ob = new Test();
int a = 15, b = 20;
System.out.println("a and b before call: " +a + " " + b);
ob.meth(a, b);
System.out.println("a and b after call: " +a + " " + b);
}
}](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-136-320.jpg)
![public class GarbageCollector{
public static void main(String[] args) {
int SIZE = 200;
StringBuffer s;](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-141-320.jpg)
![Creating Strings
3 ways to create strings:
String s;
s = “Hello”;
String s = “Hello”;
We can create an object to String class by allocating memory
using new operator.
String s = new String(“Hello”);
Creating string by converting character arrays into strings.
char arr[ ] = { ‘h’, ‘e’, ‘l’, ‘l’ , ‘o’};
Now create string object by passing the array name to it as,
String s = new String (arr);](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-144-320.jpg)
![ String s= new String();
String(char chars[])
String(char chars[], int startIndex, int numChars)
String(String strobj)
String str=new String(“SNIST”);
String str[]=new String[size];
String Constructors](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-146-320.jpg)
![String Constructors
String s= new String(); //To create an empty String call the default constructor.
String(char chars[]) //To create a string initialized by an array of characters.
String str = "abcd"; is equivalent to
char chars[]={‘a’,’b’,’c’,’d’};
String s=new String(chars);
String( char chars[], int startIndex, int numChars) //To create a string by specifying
positions from an array of characters
char chars[]={‘a’,’b’,’c’,’d’,’e’,’f’};
String s=new String(chars,2,3); //This initializes s with characters “cde”.
String(String str); //Construct a string object by passing another string object.
String str = "abcd";
String str2 = new String(str);
String(byte asciiChars[ ]) // Construct a string from subset of byte array.
String(byte asciiChars[ ], int startIndex, int numChars)](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-147-320.jpg)
![// Construct one String from another.
class MakeString {
public static void main(String args[])
{
char c[] = {'J', 'a', 'v', 'a'};
String s1 = new String(c);
String s2 = new String(s1);
System.out.println(s1);
System.out.println(s2);
}
}
Output:
Java
Java
// Construct string from subset of char array.
class SubStringCons {
public static void main(String args[])
{
byte ascii[] = {65, 66, 67, 68, 69, 70 };
String s1 = new String(ascii);
System.out.println(s1);
String s2 = new String(ascii, 2, 3);
System.out.println(s2);
}
}
Output:
ABCDEF
CDE](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-148-320.jpg)
![String Length
char chars[] = { 'a', 'b', 'c' };
String s = new String(chars);
System.out.println(s.length()); //it returns 3.](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-149-320.jpg)
![Special String Operations
String Conversion using toString( )
// Override toString() for Box class.
class Box {
double width;
double height;
double depth;
Box(double w, double h, double d) {
width = w;
height = h;
depth = d;
}
public String toString() {
return "Dimensions are " + width + " by "
+depth + " by " + height + ".";
}
}
class toStringDemo {
public static void main(String args[]) {
Box b = new Box(10, 12, 14);
String s = "Box b: " + b;
// concatenate Box object
System.out.println(b);
// convert Box to string
System.out.println(s);
}
}
The output of this program is shown here:
Dimensions are 10.0 by 14.0 by 12.0
Box b: Dimensions are 10.0 by 14.0 by 12.0
Box’s toString() method is automatically invoked when a Box object is used in a
concatenation expression or in a call to println( ).](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-152-320.jpg)
![Character Extraction
char charAt(int where)
//To extract a single character from a String
char ch;
ch = "abc".charAt(1);
//assigns the value “b” to ch.
void getChars(int sourceStart, int sourceEnd, char
target[ ], int targetStart)
//to extract more than one character at a time.
byte[ ] getBytes( )
//to store the characters in an array of bytes and it
uses the default character-to-byte conversions
provided by the platform.
//String source=“hi”+”how”+”are”+”you.”
//byte buf[] = source.getBytes();
char[ ] toCharArray( )
//to convert all the characters in a String object into a
character array. It returns an array of characters for
the entire string.
class getCharsDemo {
public static void main(String args[]) {
String s = "This is a demo of the
getChars method.";
int start = 10;
int end = 14;
char buf[] = new char[end - start];
s.getChars(start, end, buf, 0);
System.out.println (buf);
}
}
Here is the output of this program: demo](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-153-320.jpg)
![class GetBytesDemo{
public static void main(String[] args){
String str = "abc” + “ABC”;
byte[] b = str.getBytes();
//char[] c=str.toCharArray();
System.out.println(str);
for(int i=0;i<b.length;i++){
System.out.print(b[i]+" ");
//System.out.print(c[i]+" ");
}
}
}
Output:
97 98 99 65 66 67
//a b c A B C](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-154-320.jpg)
![String Comparison
boolean equals(Object str)
//To compare two strings for equality. It returns true if the strings contain the same
characters in the same order, and false otherwise.
boolean equalsIgnoreCase(String str)
//To perform a comparison that ignores case differences.
// Demonstrate equals() and
equalsIgnoreCase().
class equalsDemo {
public static void main(String args[])
{
String s1 = "Hello";
String s2 = "Hello";
String s3 = "Good-bye";
String s4 = "HELLO";
System.out.println(s1.equals(s2));
System.out.println(s1.equals(s3));
System.out.println(s1.equals(s4));
System.out.println(s1.equalsIgnoreCase(s4));
}
}
The output from the program is shown here:
true
false
false
true](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-155-320.jpg)
![class RegionTest{
public static void main(String args[]){
String str1 = "This is Test";
String str2 = “THIS IS TEST";
if(str1.regionMatches(5,str2,5,3)) {
// Case, pos1,secdString,pos1,len
System.out.println("Strings are Equal");
}
else{
System.out.println("Strings are NOT Equal");
}
}
}
Output:
Strings are NOT Equal
String Comparison](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-157-320.jpg)
![// equals() vs ==
class EqualsNotEqualTo {
public static void main(String args[]) {
String s1 = "Hello";
String s2 = new String(s1);
//String s2 = s1;
System.out.println(s1.equals(s2));
System.out.println( s1 == s2);
}
}
Output:
true
false
String Comparison](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-159-320.jpg)
![class SortString {
static String arr[] = {
"Now", "is", "the", "time", "for", "all", "good", "men",
"to", "come", "to", "the", "aid", "of", "their", "country“};
public static void main(String args[]) {
for(int j = 0; j < arr.length; j++) {
for(int i = j + 1; i < arr.length; i++) {
if(arr[i].compareTo(arr[j]) < 0) {
String t = arr[j];
arr[j] = arr[i];
arr[i] = t;
}
}
System.out.println(arr[j]);
}
}
}
The output of this program is the list of words:
Now aid all come country for good is men of
the the their time to to
String Comparison](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-161-320.jpg)
![// Demonstrate indexOf() and lastIndexOf().
class indexOfDemo {
public static void main(String args[]) {
String s = "Now is the time for all good men " +"to
come to the aid of their country.";
System.out.println(s);
System.out.println("indexOf(t) = " +s.indexOf('t'));
System.out.println("lastIndexOf(t) = " +s.lastIndexOf('t'));
System.out.println("indexOf(the) = " +s.indexOf("the"));
System.out.println("lastIndexOf(the) = " +s.lastIndexOf("the"));
System.out.println("indexOf(t, 10) = " +s.indexOf('t', 10));
System.out.println("lastIndexOf(t, 60) = " +s.lastIndexOf('t', 60));
System.out.println("indexOf(the, 10) = " +s.indexOf("the", 10));
System.out.println("lastIndexOf(the, 60) = " +s.lastIndexOf("the", 60));
}
}
Here is the output of this program:
Now is the time for all good men
to come to the aid of their country.
indexOf(t) = 7
lastIndexOf(t) = 65
indexOf(the) = 7
lastIndexOf(the) = 55
indexOf(t, 10) = 11
lastIndexOf(t, 60) = 55
indexOf(the, 10) = 44
lastIndexOf(the, 60) = 55](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-163-320.jpg)
![// Substring replacement.
class StringReplace {
public static void main(String args[]) {
String org = "This is a test. This is, too.";
String result = org.substring(0, 2);
System.out.println(result);
}
}
Output:
Th
Modifying a String
String substring(int startIndex)
//To extract a substring, startIndex specifies the beginning index
String substring(int startIndex, int endIndex)
// Here endIndex specifies the stopping point.
//endIndex-1](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-164-320.jpg)
![Data Conversion Using valueOf( )
static String valueOf(double num)
// converts data from its internal format into a human-readable form.
static String valueOf(long num)
//each type can be converted properly into a string
static String valueOf(Object ob)
static String valueOf(char chars[ ])](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-166-320.jpg)
![Changing the Case of Characters Within a String
String toLowerCase( )
//converts all the characters in a string from uppercase to lowercase.
String toUpperCase( )
//converts all the characters in a string from lowercase to uppercase
// Demonstrate toUpperCase() and toLowerCase().
class ChangeCase {
public static void main(String args[]){
String s = "This is a test.";
System.out.println("Original: " + s);
String upper = s.toUpperCase();
String lower = s.toLowerCase();
System.out.println("Uppercase: " + upper);
System.out.println("Lowercase: " + lower);
}
}
Output:
Original: This is a test.
Uppercase: THIS IS A TEST.
Lowercase: this is a test.](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-167-320.jpg)
![// StringBuffer length vs. capacity.
class StringBufferDemo {
public static void main(String args[]) {
StringBuffer sb = new StringBuffer("Hello");
System.out.println("buffer = " + sb);
System.out.println("length = " + sb.length());
System.out.println("capacity = " + sb.capacity());
}
}
Output:
buffer = Hello
length = 5
capacity = 21
int length( ) //The current length of a StringBuffer can be found via the length( ) method
int capacity( ) //The total allocated capacity can be found through the capacity( ) method.](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-171-320.jpg)
![// Demonstrate charAt() and setCharAt().
class setCharAtDemo {
public static void main(String args[]) {
StringBuffer sb = new StringBuffer("Hello");
System.out.println("buffer before = " + sb);
System.out.println("charAt(1) before = " + sb.charAt(1));
sb.setCharAt(1, 'i');
sb.setLength(2);
System.out.println("buffer after = " + sb);
System.out.println("charAt(1) after = " + sb.charAt(1));
}
}
void setLength(int len) //To set the length of the buffer within a StringBuffer object.
char charAt(int where)
//The value of a single character can be obtained from a StringBuffer via
the charAt( ) method.
void setCharAt(int where, char ch)
//To set the value of a character, ch specifies the new value of that character.
Output:
buffer before = Hello
charAt(1) before = e
buffer after = Hi
charAt(1) after = i](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-172-320.jpg)
![ void getChars(int sourceStart, int sourceEnd, char target[ ], int
targetStart)
// To copy a substring of a StringBuffer into an array
StringBuffer append(String str)
// concatenates the string representation of any other type of data to the
end of the invoking StringBuffer object.
StringBuffer append(int num)
StringBuffer append(Object obj)
String.valueOf( ) is called for each parameter to obtain its string
representation. The result is appended to the current StringBuffer
object.](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-173-320.jpg)
![// Demonstrate append().
class appendDemo {
public static void main(String args[]) {
String s;
int a = 42;
StringBuffer sb = new StringBuffer(40);
s = sb.append("a = ").append(a).append("!").toString();
System.out.println(s);
}
}
Output:
a = 42!](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-174-320.jpg)
![//The insert( ) method inserts one string into another.
StringBuffer insert(int index, String str)
StringBuffer insert(int index, char ch)
StringBuffer insert(int index, Object obj)
// Demonstrate insert().
class insertDemo {
public static void main(String args[]) {
StringBuffer sb = new StringBuffer("I Java!");
sb.insert(2, "like ");
System.out.println(sb);
}
}
Output:
I like Java!](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-175-320.jpg)
![StringBuffer reverse( )
// reverse the characters within a StringBuffer object using reverse( )
// Using reverse() to reverse a StringBuffer.
class ReverseDemo {
public static void main(String args[]) {
StringBuffer s = new StringBuffer("abcdef");
System.out.println(s);
s.reverse();
System.out.println(s);
}
}
Output:
abcdef
fedcba](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-176-320.jpg)
![StringBuffer delete(int startIndex, int endIndex) // to delete characters.
StringBuffer deleteCharAt(int loc)
// Demonstrate delete() and deleteCharAt()
class deleteDemo {
public static void main(String args[]) {
StringBuffer sb = new StringBuffer("This is a test.");
sb.delete(4, 7);
System.out.println("After delete: " + sb);
sb.deleteCharAt(0);
System.out.println("After deleteCharAt: " + sb);
}
}
Output:
After delete: This a test.
After deleteCharAt: his a test.](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-177-320.jpg)
![StringBuffer replace(int startIndex, int endIndex, String str);
//It replaces one set of characters with another set inside a StringBuffer object.
// The replacement string is passed in str.
// Demonstrate replace()
class replaceDemo {
public static void main(String args[]) {
StringBuffer sb = new StringBuffer("This is a test.");
sb.replace(5, 7, "was");
System.out.println("After replace: " + sb);
}
}
Output: After replace: This was a test.
String substring(int startIndex) //to return sub strings.
String substring(int startIndex, int endIndex)](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-178-320.jpg)
![// Demonstrate StringTokenizer.
import java.util.StringTokenizer;
class STDemo{
//static String str = "Hello Welcome to Java Programming";
static String str = "Hello,Welcome,to,Java,Programming";
public static void main(String args[]) {
//StringTokenizer st = new StringTokenizer(str);
//StringTokenizer st = new StringTokenizer(str,",");
StringTokenizer st = new StringTokenizer(str,",",true);
while(st.hasMoreTokens()) {
String tokens = st.nextToken();
System.out.println(tokens + "n");
}
}
}
Output:
Hello
,
Welcome
,
to
,
Java
,
Programming](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-181-320.jpg)
![import java.util.Scanner;
import java.util.*;
class Token{
static int sum=0;
public static void main(String sree[]){
Scanner s=new Scanner(System.in);
System.out.print("Enter sum of integers: ");
String str=s.next();
StringTokenizer st=new StringTokenizer(str,"+");
while(st.hasMoreTokens()){
sum=sum+Integer.parseInt(st.nextToken());
}
System.out.println("Sum of "+str+“is: "+sum);
}
}
Output:
Enter sum of integers: 10+20+30+40
Sum of 10+20+30+40 is: 100](https://image.slidesharecdn.com/java1-151017132424-lva1-app6892/85/Java1-183-320.jpg)
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Java1
- 2. Software Software is a collection of programs as a solution to the real time problems. A Program is a set of instructions with syntax and semantics. We write programs by using a programming language.
- 3. Programming Languages Machine Language It contains 0’s and 1’s. Machine understandable form Difficult to write programs for human Assembly Language Microprocessor Language Contains pneumonics High Level Language Procedures and functions Object oriented programs are also high level. Ex: PASCAL, COBOL,FORTRAN, C, C++, JAVA
- 4. Programming Styles Three different programming styles. Top-down Bottom – Up Modules Top-down The main method appears at top of the program. The compilation begins from top. Bottom-up The functions or classes will be defined first, followed by main method. The compilation starts from the main, that is available at bottom and goes to top.
- 5. Network, Types of Networks, Protocols
- 6. what is Java? Java is an Object Oriented Programming Language. In Java, we can write two types of programs. Console Applications These programs result will displays at command prompt. Applets / Web Programs The program result will displays in the web browser.
- 7. Relation between java and network
- 8. History of Java Java started out as a research project to manipulate consumer electronic devices. Research began in 1991 as the Green Project at Sun Microsystems, under the lead of James Gosling. Research efforts birthed a new language, OAK. ( A tree outside the window of James Gosling’s office at Sun) It was developed as an embedded programming language, which would enable embedded system application.
- 9. History of Java With the invention of www in 1993, The team developed web applets to run on network of computers. The team developed a web browser called HotJava in 1994. Java is available as jdk from 1995 and it is an open source s/w.
- 10. From the History of Java Language was created with 5 main goals: It should be object oriented. A single representation of a program could be executed on multiple operating systems. (i.e. write once, run anywhere) It should fully support network programming. It should execute code from remote sources securely. It should be easy to use.
- 11. James Gosling
- 12. Green Team
- 13. Java Logo
- 14. Versions of Java Version Year Features Added JDK 1.1 Feb19,1997 Inner classes JavaBeans, JDBC, RMI, Reflection, AWT. J2SE 1.2 Dec8, 1998 JIT compiler, Collections, IDL & CORBA, strictfp, Java Plug-in. J2SE 1.3 May8, 2000 HotSpot JVM, JavaSound, Java Naming and Directory Interface, Java Platform Debugger Architecture. J2SE 1.4 Feb6, 2002 Preferences API, Logging API, assert, image I/O API, security and cryptography extensions. J2SE 5.0 Sep30, 2004 Generics, annotations, Autoboxing, Enumerations, Varargs, Enhanced for each. JAVA SE 6 Dec11, 2006 JDBC 4.0, JVM improvements, Improved web services, Support for older Win9x versions dropped.
- 15. Java Platforms There are three main platforms for Java: Java SE (Java Platform, Standard Edition) – runs on desktops and laptops. Java ME (Java Platform, Micro Edition) – runs on mobile devices such as cell phones. Java EE (Java Platform, Enterprise Edition) – runs on servers.
- 16. Java Development Kit: (Jdk) It contains JRE's along with the various development tools like the Java source compilers, bundling and deployment tools, debuggers, development libraries, etc. Tools of jdk • javac ( java compiler) • java (java interpreter) • appletviewer • jdb (java debugger) Java Terminology
- 17. javadoc creates html format documentation for java source code. javap java disassembler, that converts bytecode into program description Java Virtual Machine: (JVM) It interprets the byte code into the machine code depending upon the underlying OS and hardware combination. It uses the class libraries, and other supporting files provided in JRE Java Terminology
- 18. Java Runtime Environment: A runtime environment which implements Java Virtual Machine, and provides all class libraries and other facilities necessary to execute Java programs. This is the software on your computer that actually runs Java programs. JRE = JVM + Java Packages Classes (like util, math, lang, awt, swing etc) +runtime libraries. Java Terminology
- 19. Object Oriented Programming Concepts Objects Classes Data abstraction and Encapsulation Inheritance Polymorphism Dynamic Binding
- 20. A class is collection of objects of similar type or it is a template. Ex: fruit mango; Objects are instances of the type class. The wrapping up of data and functions into a single unit ( called class) is known as encapsulation. Data encapsulation is the most striking features of a class. Abstraction refers to the act of representing essential features without including the background details or explanations Inheritance is the process by which objects of one class acquire the properties of another class. The concept of inheritance provides the reusability. class object
- 21. Polymorphism: It allows the single method to perform different actions based on the parameters. Dynamic Binding: When a method is called within a program, it associated with the program at run time rather than at compile time is called dynamic binding.
- 22. Object-Oriented Languages Types 1.Object-based programming language: It supports Data encapsulation Data hiding and access mechanisms Automatic initialization and clear-up of objects Operator overloading Disadvantage : They do not support inheritance and dynamic binding Ex: Ada 2.Object-oriented programming languages: OOP = Object-based + inheritance + dynamic binding Ex: C++, Java, Smalltalk, Object Pascal
- 23. Benefits of OOP Through inheritance, we can eliminate redundant code and extend the use of existing classes. The principle of data hiding helps the programmer to build secure programs. It is easy to partition the work in a project based on objects. Object oriented system easily upgraded from small to large systems. Software complexity can be easily managed.
- 24. Applications of oop Real-time systems Object-oriented databases Neural networks and parallel programming Decision support and office automation systems CAD/CAM systems
- 25. C++ Vs. Java C++ Java Supports operator overloading Doesn’t support operator overloading Template classes are available. No templates
- 26. C++ Vs. Java C++ Java
- 27. Features of Java (Java Buzz Words) Simple Object Oriented Distributed Robust Secure System independence & Portable Compile, Interpreted and High Performance Multithreaded Dynamic Architecture-Neutral
- 28. Java Features Simple The design goal of java is simple. Pointers are eliminated in java. Improper handling of pointers leads to memory leaks and reliability issues. Pointers may crash a program easily. For ex: when we add two pointers the program crashes immediately. Pointers break security over internet. Rich pre-defined class libraries through packages Object Oriented Every thing (primitive types, arrays, void including static variable and static methods ) will be represented as objects of class. Java follows all features of OOP language. All methods are associated with objects
- 29. Distributed Java is designed for the distributed environment of the Internet, because it handles TCP/IP protocols. Allows objects on two different computers to execute procedures remotely by using package called Remote Method Invocation (RMI) Robust Robust means strong. Inbuilt exception handling features. Memory management feature. Automatic garbage collection tracks objects usage over time and deletes if the variable or an object is not used. Java Features
- 30. Java Features Secure Security problems and virus threats can be eliminated or minimized with java programs (firewalls) over internet. Access restrictions are forced (private, public) System independence Byte code is not machine dependent. It can run on any processor and any operating system. Portability Same application runs on all platforms The sizes of the primitive data types are always the same
- 31. Java Features Compile, Interpreted and High Performance Java compiler generate byte-code, not native machine code The byte-codes are platform-independent Java byte code is translated to machine readable instructions in runtime (Java Virtual Machine) Easy to translate directly into native machine code by using a just-in-time compiler, which enhances the speed of execution. Multithreaded A thread is an individual process. JVM supports multithreaded programming. Need not wait for the application to finish one task before beginning another one.
- 32. Java Features Dynamic Libraries can freely add new methods and instance variables without any effect on their clients Interfaces promote flexibility and reusability in code by specifying a set of methods an object can perform, but leaves open how these methods should be implemented . Architecture-Neutral Goal of java designers is “write once; run anywhere, any time, forever.”
- 33. Java Program Structure Documentation Section Package Statement Import Statement Interface Statements Class Definition Main method class { main method definition } Suggested Optional Essential Optional compulsory Optional
- 34. Starting a Java Program (Sample) import java.lang.System; import java.lang.String; or use import java. lang.*; class First { public static void main (String args []) { System.out.println (“Welcome to Java”); } }
- 35. Starting a Java Program (Sample) Explanation First , decide and import the classes, which are required for the program. Group of classes and interfaces with its methods are contained in a package. Java has several such packages in its library. java library Packages Classes and interfaces Methods In java.lang.* , * means all the classes and interfaces of that package are make available into our program.
- 37. System is a class which is present in java.lang package. out is a static field present in system class which returns a PrintStream object. As out is a static field it can call directly with classname. println() is a method which present in PrintStream class which can call through the PrintStream object return by static field out present in System class to print a line to console.
- 38. Single Line comments: Starts with // double slash symbol. Multi Line comments: Stars with /* and ends with */ Java documentation comments: Starts with /** and end with */. These comments are used to provide description for every feature in a java program. Comments
- 39. Formatting the Output n Next line t Horizontal tab space r Enter key b Back space f Form feed Displays ” Displays” ’ Displays’
- 40. The Architecture of the Java Virtual Machine Operating System Interpreter & JIT
- 41. W Java Sour ce Class Loader Byte Code Verifier Java Class Librari es Java Interp reter Just-in- time Compil er Run Time System Java OS Win 32 Solari s MAC Other s Hardware Java Execution Procedure
- 42. Binary form of a class file public class Hello { public static { System.out.println("Hello, World!"); } }
- 43. Keywords abstract continue goto package synchronized assert default if private this boolean do implements protected throw break double import public throws byte else instanceOf return transient case extends int short try catch final interface static void char finally long strictfp volatile class float native super while const for new switch
- 44. Data Types Simple Type Derived Type User Defined Type Numeric Type Non-Numeric class Interface Integer Float Char Boolean float double byte short int long E.g: Array, String… Single precision Double precision
- 45. Data Types Java Is a Strongly Typed Language Every variable has a type, every expression has a type, and every type is strictly defined. All assignments, whether explicit or via parameter passing in method calls, are checked for type compatibility. There are no automatic conversions of conflicting types as in some languages. For example, in C/C++ you can assign a floating-point value to an integer. In Java, you cannot.
- 46. Integer Data Types Java does not support unsigned, positive-only integers. All are signed, positive and negative values. Byte Data Type The smallest integer type is byte. Variables of type byte are especially useful while working with a stream of data from a network or file. Byte variables are declared by use of the byte keyword. Ex: byte b, c; Floating Point Types There are two kinds of floating-point types. All math functions, such as sin( ), cos( ), and sqrt( ), return double values. Boolean Data Type It can have only one of two possible values, true or false. This is the type, returned by all relational operators, such as a < b.
- 47. Character Data Type char in Java is not the same as char in C or C++. Java uses Unicode to represent characters. Unicode defines a fully international character set that can represent all of the characters found in all human languages. It is a unification of dozens of character sets, such as Latin, Greek, Arabic, Cyrillic, Hebrew, Katakana, Hangul, and many more. Hence it requires 16 bits. The range of a char in java is 0 to 65,536. There are no negative chars.
- 48. Data Types Name Width in bits Range long 64 –9,223,372,036,854,775,808 to 9,223,372,036,854,775,807 int 32 –2,147,483,648 to 2,147,483,647 short 16 –32,768 to 32,767 byte 8 –128 to 127 double 64 4.9e–324 to 1.8e+308 float 32 1.4e−045 to 3.4e+038 char 16 0 to 65,536.
- 49. public class IntDemo{ public static void main(String args[]){ System.out.println(" For an Integer "); System.out.println("Size is : "+Integer.SIZE); int i1 = Integer.MAX_VALUE; int i2 = Integer.MIN_VALUE ; System.out.println("Max value is : "+i1); System.out.println("Min Value is : "+i2); System.out.println(" For an Byte"); System.out.println("Size is : "+Byte.SIZE); byte b1 = Byte.MAX_VALUE; byte b2 = Byte.MIN_VALUE ; System.out.println("Max value is : "+b1); System.out.println("Min Value is : "+b2); System.out.println(" For an Short"); System.out.println("Size is : "+Short.SIZE); short s1 = Short.MAX_VALUE; short s2 = Short.MIN_VALUE ; System.out.println("Max value is : "+s1); System.out.println("Min Value is : "+s2); System.out.println(" For a Long"); System.out.println("Size is : "+Long.SIZE); long l1 = Long.MAX_VALUE; long l2 = Long.MIN_VALUE ; System.out.println("Max value is : "+l1); System.out.println("Min Value is : "+l2); } }
- 50. public class FloatDemo{ public static void main(String args[]){ System.out.println(" For an Float"); System.out.println("Size is : "+Float.SIZE); float f1 = Float.MAX_VALUE; float f2 = Float.MIN_VALUE ; System.out.println("Max value is : "+f1); System.out.println("Min Value is : "+f2); System.out.println(" For an Double"); System.out.println("Size is : "+Double.SIZE); double d1 = Double.MAX_VALUE; double d2 = Double.MIN_VALUE ; System.out.println("Max value is : "+d1); System.out.println("Min Value is : "+d2); } }
- 51. public class CharDemo{ public static void main(String args[]){ System.out.println(" For a Char"); System.out.println("Size is : "+Character.SIZE); int f1 = Character.MAX_VALUE; long f2 = Character.MIN_VALUE ; System.out.println("Max value is : "+f1); System.out.println("Min Value is : "+f2); } }
- 52. Variables The variable is the basic unit of storage in a Java program. A variable is defined by the combination of an identifier, a type, and an optional initializer. Declaring a Variable In Java, all variables must be declared before they can be used. type identifier [ = value][, identifier [= value] ...] ; Types Instance Variable Class Variable Local Variable Parameters
- 53. Local variables : • Local variables are declared in methods, constructors, or blocks.
- 54. Instance variables : • Instance variables are declared in a class, but outside a method, constructor or any block. • Instance variables are created when an object is created with the use of the key word 'new' and destroyed when the object is destroyed. • Access modifiers can be given for instance variables. • The instance variables are visible for all methods, constructors and block in the class. • Instance variables have default values. • Instance variables can be accessed directly by calling the variable name inside the class. • However within static methods and different class ( when instance variables are given accessibility) that should be called using the fully qualified name ObjectReference.VariableName
- 55. Class/Static variables : • Class variables also known as static variables are declared with the static keyword in a class, but outside a method, constructor or a block. • There would only be one copy of each class variable per class, regardless of how many objects are created from it. • Static variables are stored in static memory. • Static variables are created when the program starts and destroyed when the program stops. • Visibility is similar to instance variables. • Default values are same as instance variables. • Static variables can be accessed by calling with the class name ClassName.VariableName
- 56. class Variables{ int i; public int j static long l=10; public static float f; char c; boolean b; void display(int a){ i=a; System.out.println("i value in display: "+i); } public static void main(String args[]){ double d=0.0; //public double d=0.0; invalid Variables v1=new Variables(); Variables v2=new Variables(); Variables v3=new Variables(); v1.display(100); v1.i=2; v2.i=3; v3.i=4; System.out.println("i value is: "+v1.i); System.out.println("i value is: "+v2.i); System.out.println("i value is: "+v3.i); System.out.println("i value is: "+v1.j); v1.l=20; v2.l=30; v3.l=40; System.out.println("l value is: "+v1.l); System.out.println("l value is: "+v2.l); System.out.println("l value is: "+v3.l); System.out.println("f value is: "+f); System.out.println("c value is: "+v1.c); System.out.println("b value is: "+v1.b); System.out.println("d value is: "+d); } }
- 57. class Variables{ int i;//instance variable public int j ;//instance variable static long l=10;//class variable public static float f;//class variable char c;//instance variable boolean b;//instance variable void display(int a){ i=a; System.out.println("i value in display: "+i); } public static void main(String args[]){ double d=0.0;//local varible //public double d=0.0; invalid Variables v1=new Variables(); Variables v2=new Variables(); Variables v3=new Variables(); v1.display(100); v1.i=2; v2.i=3; v3.i=4; System.out.println("i value is: "+v1.i); System.out.println("i value is: "+v2.i); System.out.println("i value is: "+v3.i); System.out.println("i value is: "+v1.j); v1.l=20; v2.l=30; v3.l=40; System.out.println("l value is: "+v1.l); System.out.println("l value is: "+v2.l); System.out.println("l value is: "+v3.l); System.out.println("f value is: "+f); System.out.println("c value is: "+v1.c); System.out.println("b value is: "+v1.b); System.out.println("d value is: "+d); } }
- 58. Variables declared inside a scope are not accessible to code outside. Scopes can be nested. The outer scope encloses the inner scope. Variables declared in the outer scope are visible to the inner scope. Variables declared in the inner scope are not visible to the outside scope.
- 59. Operators Arithmetic Operators Relational Operators Logical Operators Assignment Operators Increment and decrement operators Conditional Operators Bitwise Operators Special Operators
- 60. Arithmetic Operators Operator Result + Addition – Subtraction * Multiplication / Division % Modulus
- 61. Relational Operators The relational operators determine the relationship that one operand has to the other. They determine equality and ordering. Operator Result == Equal to != Not equal to > Greater than < Less than >= Greater than or equal to <= Less than or equal to
- 62. Logical Operators Operator Result && Logical AND | | Logical OR ^ Logical XOR (exclusive OR) || Short-circuit OR && Short-circuit AND ! Logical unary NOT
- 63. & //executes both left and right side operands && // Java will not bother to evaluate the right-hand operand when the outcome of the expression can be determined by the left operand alone. class Test{ public static void main(String args[]){ int denom=0,num=20; if (denom != 0 && num / denom > 10) System.out.println("Hi"); } }
- 64. Boolean Logical Operators(2) Operator Result &= AND assignment |= OR assignment ^= XOR assignment == Equal to != Not equal to ?: Ternary if-then-else
- 65. Assignment Operator Operator Result += Addition assignment – = Subtraction assignment *= Multiplication assignment /= Division assignment %= Modulus assignment
- 66. Increment / Decrement Operator Operator Result ++ Pre / Post increment -- Pre / Post Decrement
- 67. Example: class IncDec{ public static void main(String args[]){ int a = 1; int b = 2; int c,d; c = ++b; d = a++; c++; System.out.println("a = " + a); System.out.println("b = " + b); System.out.println("c = " + c); System.out.println("d = " + d); } }
- 68. class OpEquals{ public static void main(String args[]){ int a = 1; int b = 2; int c = 3; a += 5; b *= 4; c += a * b; c %= 6; System.out.println("a = " + a); System.out.println("b = " + b); System.out.println("c = " + c); } }
- 69. Bitwise Operators(1) bitwise operators can be applied to the integer types, long, int, short, byte and char. These operators act upon the individual bits of their operands. Operator Result ~ Bitwise unary NOT & Bitwise AND | Bitwise OR ^ Bitwise exclusive OR >> Shift right >>> Shift right zero fill << Shift left
- 70. Bitwise Operators(2) Operator Result &= Bitwise AND assignment |= Bitwise OR assignment ^= Bitwise exclusive OR assignment >>= Shift right assignment >>>= Shift right zero fill assignment <<= Shift left assignment
- 71. 00101010 42 &00001111 15 -------------- 00001010 10 00101010 42 ^00001111 15 ------------- 00100101 37 int a = 32; a = a >> 2; 8 int a = 64; a = a << 2; 256 11111000 –8 >>1 11111100 –4 11111111 11111111 11111111 11111111 –1 >>>24 00000000 00000000 00000000 11111111 255
- 72. Example: public class RelationalOperatorsDemo { public static void main(String args[]) { int x=10,y=5; System.out.println(“x>y:”+(x>y)); System.out.println(“x<y:”+(x<y)); System.out.println(“x>=y:”+(x>=y)); System.out.println(“x<=y:”+(x<=y)); System.out.println(“x==y:”+(x==y)); System.out.println(“x!=y:”+(x!=y)); } }
- 74. public class TernaryOperatorDemo { public static void main(String args[]) { int x=10,y=12; int z; z= x > y ? x : y; System.out.println(“Z=“+z); }
- 76. Expressions An expression is a combination of constants (like 10), operators ( like +), variables(section of memory) and parentheses ( like “(” and “)” ) used to calculate a value. Ex1: x = 1; Ex2: y = 100 + x; Ex3: x = (32 - y) / (x + 5)
- 77. public class TernaryOperatorDemo { public static void main(String args[ ]) { int x=10,y=12; int z; z= x > y ? x : y; System.out.println(“Z=“+z); }
- 79. Expressions An expression is a combination of constants (like 10), operators ( like +), variables(section of memory) and parentheses ( like “(” and “)” ) used to calculate a value. Ex1: x = 1; Ex2: y = 100 + x; Ex3: x = (32 - y) / (x + 5)
- 80. Control Statements Selection Statements: if & switch Iteration Statements: for, while and do-while Jump Statements: break, continue and return
- 81. Selection Statements if (condition) statement1; else statement2; if(condition) statement; else if(condition) statement; else if(condition) statement; ... else statement; switch (expression) { case value1: // statement sequence break; case value2: // statement sequence break; … case valueN: // statement sequence break; default: // default statement sequence }
- 82. The condition is any expression that returns a boolean value. The expression must be of type byte, short, int, or char; Each of the values specified in the case statements must be of a type compatible with the expression.
- 83. Iteration Statements while(condition) { // body of loop } do { // body of loop } while (condition); for(initialization; condition; iteration) { // body }
- 84. for – each loop This loop is specifically designed to handle the elements of a collection. Collection represents a group of elements.
- 85. Example for for-each class demo { public static void main(String args[]) { } } }
- 86. Jump Statements break; //exit from the loop continue; //bypass the followed instructions return; //control returns to the caller label: - - - - - - - - break label; //it’s like goto statement
- 87. break, continue and return statements break: Used inside of a loop to come out of it. Used inside switch block to come out of it. Used in nested blocks to go to the end of the block. Continue: Used inside the loop to repeat the next iteration of loop. When continue is executed, subsequent statements in the loop are not executed and control goes back to the next repetition of the loop. Return statement is used in a method to come out of it to the calling method.
- 88. Example for continue class continuedemo { public static void main(String args[]) { ; } } }
- 89. Type Conversion and Casting Type conversion, typecasting, refers to different ways of, implicitly or explicitly, changing an entity of one data type into another. Types of Conversions: 1.Widening conversion 2.Narrowing conversion
- 90. Widening Conversion The widening conversion is permitted in the following cases: byte to short, int, long, float, or double short to int, long, float, or double char to int, long, float, or double int to long, float, or double long to float or double float to double
- 91. When one type of data is assigned to another type of variable, an automatic type conversion will take place if the following two conditions are met: The two types are compatible. The destination type is larger than the source type. When these two conditions are met, a widening conversion takes place. Ex: char and boolean are not compatible with each other.
- 93. In general, the narrowing primitive conversion can occur in these cases: short to byte or char char to byte or short int to byte, short, or char long to byte, short, or char float to byte, short, char, int, or long double to byte, short, char, int, long, or float Narrowing conversion is used to cast the above incompatible types. (target-type) value Narrowing Conversion
- 95. Arrays An array is a group of homogeneous (same type of) elements that are referred by a common name. In java, Arrays are created on dynamic memory by JVM. The operator new is used for dynamic memory allocation. One-Dimensional Arrays: Syntax: type variablename[] = {elements list}; ex: int marks[] = {60,70,80,50}; Syntax : type varname[]=new type[size]; int month[] = new int[12];
- 96. Multidimensional Arrays int twoD[][]=new int[4][5];
- 97. If month is a reference to an array, month.length will gives the length of the array. Initialization: char []c = {‘a’, ‘b’, ‘c’}; double d[][]= { {1.0,2.0,3.0}, {4.0,5.0,6.0}, {7.0,8.0,9.0} };
- 100. Jagged Arrays X[0] [0] x[0] [1] X[1] [0] x[1] [1] x[1] [2]
- 102. Command Line Arguments Values passed by the user at runtime from command prompt are command line arguments. Represent values passed to main method. To store these values main has a parameter, String args[ ] For ex: c:java prog 22 33 anil These three values automatically stored in main() method’s args[ ] in the form of strings.
- 103. Ex program
- 104. Concepts of Classes, Objects
- 105. Class Group of similar objects. It is a model to create objects. The properties and actions of the objects are written in the class. Properties are represented by variable and actions are represented by methods. The variables defined inside a class are called as instance variables because each object of the class contains its own copy of these variables. An object is an instance of a class.
- 106. General form of a class class classname { type instance –variable 1; type instance- variable 2; … type instance –variable N; type methodname1(parameter-list) { statements of method } type methodname1(parameter-list) { statements of method } …. type methodname n (parameter-list) { statements of method }
- 107. Example for a class
- 108. program with Object creation
- 109. Declaring an Object class Box{ double width; double height; double depth; } Representation 3: Assigning Object Reference Variables Box b1 = new Box(); Box b2 = b1; Representation 1: Box mybox; mybox=new Box(); Representation 2: Box mybox=new Box();
- 110. package packagename; import statement; class classname{ //instance variables; //class or static variables; /*methods(parameters){ //local variables; //object creation //statements; }*/ } import java.util.Scanner; class Demon{ int i; static double d; public static void main(String args[]){ char c=‘a’; Demon obj=new Demon(); Scanner s=new Scanner(System.in); d=s.nextDouble(); System.out.println(obj.i); System.out.println(d); System.out.println(c); } }
- 111. class classname{ //instance variables; //class or static variables; /*methods(parameters){ //local variables; //statements; }*/ } class MainCLass{ public static void main(String args[]) { //object creation //invoking methods //statements } } class Test{ char c='a'; static float f; void display(){ int i=10; System.out.println("Test:display()"); System.out.println(“c value: “+c); System.out.println(“i value: “+i); System.out.println(“f value: “+f); } } class Demo{ public static void main(String args[]){ Test t=new Test(); t.display(); System.out.println("Demo:main()"); } }
- 112. default : private: A private member is accessible only to the class in which it is defined. Use private keyword to create private members. Access Control
- 113. public: Any class, in any package has access to a class's public members. To declare a public member, use the keyword public. protected: Allows the class itself, subclasses, and all classes in the same package to access the members. To declare a protected member, use the keyword protected.
- 114. class AccessTest { public static void main(String args[]) { Test ob = new Test(); // These are OK, a and b may be accessed directly ob.a = 10; ob.b = 20; // This is not OK and will cause an error //ob.c = 100; // Error! // You must access c through its methods ob.setc(100); // OK System.out.println(ob.a + " " +ob.b + " " + ob.getc()); } } //Example for access control
- 116. A constructor is a special method that initialize the instance variables. The constructor is automatically called immediately after the object is created. A constructor has the same name as the class name in which it resides and is syntactically similar to a method. If no constructor in program .System provides its own constructor called as default constructor. Constructors doesn’t have any return type. A constructor which accepts parameters is called as parameterized constructor. Constructors can be overloaded.
- 117. Default Constructor: A constructor that accepts no parameters is called Default constructor. If not defined, provided by the compiler. The default constructor is called whenever an object is created without specifying initial values. Ex: class Box { double width; double height; double depth; Box() { width = 10; height = 10; depth = 10; } } // declare, allocate, and initialize Box objects Box mybox1 = new Box();
- 118. class Test{ char c='a'; static float f; Test(){ int i=10; System.out.println("Test:Test()"); System.out.println(“c value: “+c); System.out.println(“i value: “+i); System.out.println(“f value: “+f); } } class ConDemo{ public static void main(String args[]){ Test t=new Test(); //t.Test(); System.out.println(“ConDemo:main()"); } } class Test{ int x,y; Test(int a, int b){ x=a; y=b; System.out.println(“x value: “+x); System.out.println(“y value: “+y); } } class PConDemo{ public static void main(String args[]){ Test t=new Test(10,20); System.out.println(“PConDemo:main()"); } } //Parameterized Constructor// Default Constructor
- 119. Methods General Form: type name(parameter-list) { // body of method } The type of data returned by a method must be compatible with the return type specified by the method. The variable receiving the value returned by a method must also be compatible with the return type specified for the method. return value; //Here, value is the value returned. Ex: double volume(double w, double h, double d) { return w*h*d;
- 120. Constructors Vs. Methods Constructors Methods Used to initialize the instance variables of a class Used for general processing purpose or calculations
- 121. Types of Methods Instance Method Static Method Instance Method: that act on the instance variables of the class. Use with object form : objectname.methodname( ); Static methods don’t act upon the instance variables of a class. because the JVM first executes static methods and then only it creates objects. Declared with static. Static methods are called using classname.methodname().
- 122. Example for static method:
- 123. Static variables & Static block Static variable is a variable whose single copy in memory is sharable by all objects These variables are stored in method area of JVM. A static block is a block of statements declared as static. static { statements; }
- 124. Static variable example program
- 125. Program to test which block executes first class test { static { System.out.println(“From static block”); } public static void main(String args[ ]) { System.out.println(“From static method”); } }
- 126. class Box{ double width; double height; double depth; Box(){ width=10; height=10; depth=10; } double volume(){ return width*height*depth; } } class BoxDemo6{ public static void main(String args[]){ Box mybox1=new Box(); Box mybox2=new Box(); double vol; vol=mybox1.volume(); System.out.println("Volume is: "+vol); vol=mybox2.volume(); System.out.println("Volume is: "+vol); } } Non parameterized or default Constructor
- 127. class Box{ double width; double height; double depth; Box(double w,double h,double d){ width=w; height=h; depth=d; } double volume(){ return width*height*depth; } } class BoxDemo7{ public static void main(String args[]){ Box mybox1=new Box(10,20,15); Box mybox2=new Box(3,6,9); double vol; vol=mybox1.volume(); System.out.println("Volume is: "+vol); vol=mybox2.volume(); System.out.println("Volume is: "+vol); } } Parameterized Constructor
- 128. Method & Constructor Overloading Defining two or more methods with the same name and within the same class is called method overloading. Java uses the type and/or number of arguments to determine which version of the overloaded method to call. Constructors can also be overloaded in the same way as method overloading.
- 129. class OverloadDemo { void test() { System.out.println("No parameters"); } void test(int a) { System.out.println("a: " + a); } void test(int a, int b) { System.out.println("a and b: " + a + " " + b); } double test(double a) { System.out.println("double a: " + a); return a*a; } } class Overload { public static void main(String args[]) { OverloadDemo ob = new OverloadDemo(); double result; ob.test(); ob.test(10); ob.test(10, 20); result = ob.test(123.25); System.out.println("Result of ob.test(123.25): " + result); } } //method overloading
- 130. //Constructor Overloading class CDemo{ int value1; int value2; CDemo(){ value1 = 10; value2 = 20; System.out.println("Inside 1st Constructor"); } CDemo(int a){ value1 = a; System.out.println("Inside 2nd Constructor"); } CDemo(int a,int b){ value1 = a; value2 = b; System.out.println("Inside 3rd Constructor"); } public void display(){ System.out.println("Value1 === "+value1); System.out.println("Value2 === "+value2); } public static void main(String args[]){ CDemo d1 = new CDemo(); CDemo d2 = new CDemo(30); CDemo d3 = new CDemo(30,40); d1.display(); d2.display(); d3.display(); } }
- 131. this In java, it is illegal to declare two local variables with the same name inside the same or enclosing scopes. But you can have formal parameters to methods, which overlap with the names of the class’ instance variables. this keyword is used to refer to the current object. this can be used to resolve any name collisions that might occur between instance variables and formal variables. When a formal variable has the same name as an instance variable, the formal variable hides the instance variable. Also used in method chaining and constructor chaining.
- 132. // instance and formal variables are different class Box{ double w=5,h=5,d=5; Box(double w1,double h1,double d1){ w=w1; h=h1; d=d1; } double volume(){ return w*h*d; } } class BoxTest1{ public static void main(String args[]){ Box b=new Box(1,2,3); System.out.println("Volume is: "+b.volume()); } } Output: Volume is:6.0
- 133. // instance and formal variables are same class Box{ double w=5,h=5,d=5; Box(double w,double h,double d){ w=w; h=h; d=d; } double volume(){ return w*h*d; } } class BoxTest2{ public static void main(String args[]){ Box b=new Box(1,2,3); System.out.println("Volume is: "+b.volume()); } } Output: Volume is:125.0
- 134. //’this’ hides the instance variables class Box{ double w=5,h=5,d=5; Box(double w,double h,double d){ } double volume(){ return w*h*d; } } class BoxTest2{ public static void main(String args[]){ Box b=new Box(1,2,3); System.out.println("Volume is: "+b.volume()); } }
- 135. Parameter Passing The call-by-value copies the value of a actual parameter into the formal parameter of the method. In this method, changes made to the formal parameter of the method have no effect on the actual parameter. In call-by-reference, a reference to an actual parameter (not the value of the argument) is passed to the formal parameter. In this method, changes made to the actual parameter will affect the actual parameter used to call the method.
- 136. // Simple types are passed by value. class Test { void meth(int i, int j) { i *= 2; j /= 2; } } class CallByValue { public static void main(String args[]) { Test ob = new Test(); int a = 15, b = 20; System.out.println("a and b before call: " +a + " " + b); ob.meth(a, b); System.out.println("a and b after call: " +a + " " + b); } }
- 138. Recursion Recursion is the process of defining something in terms of itself. A method that calls itself is said to be recursive.
- 140. Garbage Collection Garbage collection done automatically in java. When an object doesn’t have reference, that object is assumed to be not required, and the memory occupied by the object can be reclaimed. Garbage collection only occurs at regular intervals during the execution of your program. We can run garbage collection on demand by calling the gc() method. public static void gc(): Initiates the garbage collection. System.gc();
- 141. public class GarbageCollector{ public static void main(String[] args) { int SIZE = 200; StringBuffer s;
- 142. finalize( ) method Sometimes an object will need to perform some action when it is destroyed. Ex: If an object is holding some non-java resource such as a file, then you might want to make sure these resources are freed before an object is destroyed. To handle such situations, Java provides a mechanism called finalization. The finalize( ) method has this general form: protected void finalize( ){ // finalization code here }
- 143. String In java a string is a sequence of characters. They are objects of type String. Once a String object has been created, we can not change the characters that comprise in the string. Strings are unchangeable once they are created so they are called as immutable. You can still perform all types of string operations. But, a new String object is created that contains the modifications. The original string is left unchanged. To get changeable strings use the class called StringBuffer. String and StringBuffer classes are declared final, so there cannot be subclasses of these classes. String class is defined in java.lang package, so these are available to all programmers automatically.
- 144. Creating Strings 3 ways to create strings: String s; s = “Hello”; String s = “Hello”; We can create an object to String class by allocating memory using new operator. String s = new String(“Hello”); Creating string by converting character arrays into strings. char arr[ ] = { ‘h’, ‘e’, ‘l’, ‘l’ , ‘o’}; Now create string object by passing the array name to it as, String s = new String (arr);
- 145. Types of string handling classes: String Once an object is created, no modifications can be done on that. StringBuffer Modifications can be allowed on created object. StringTokenizer Used to divide the string into substrings based on tokens. String and SringBuffer classes are available in java.lang package where as StringTokenizer class is available in java.util package. String Handling
- 146. String s= new String(); String(char chars[]) String(char chars[], int startIndex, int numChars) String(String strobj) String str=new String(“SNIST”); String str[]=new String[size]; String Constructors
- 147. String Constructors String s= new String(); //To create an empty String call the default constructor. String(char chars[]) //To create a string initialized by an array of characters. String str = "abcd"; is equivalent to char chars[]={‘a’,’b’,’c’,’d’}; String s=new String(chars); String( char chars[], int startIndex, int numChars) //To create a string by specifying positions from an array of characters char chars[]={‘a’,’b’,’c’,’d’,’e’,’f’}; String s=new String(chars,2,3); //This initializes s with characters “cde”. String(String str); //Construct a string object by passing another string object. String str = "abcd"; String str2 = new String(str); String(byte asciiChars[ ]) // Construct a string from subset of byte array. String(byte asciiChars[ ], int startIndex, int numChars)
- 148. // Construct one String from another. class MakeString { public static void main(String args[]) { char c[] = {'J', 'a', 'v', 'a'}; String s1 = new String(c); String s2 = new String(s1); System.out.println(s1); System.out.println(s2); } } Output: Java Java // Construct string from subset of char array. class SubStringCons { public static void main(String args[]) { byte ascii[] = {65, 66, 67, 68, 69, 70 }; String s1 = new String(ascii); System.out.println(s1); String s2 = new String(ascii, 2, 3); System.out.println(s2); } } Output: ABCDEF CDE
- 149. String Length char chars[] = { 'a', 'b', 'c' }; String s = new String(chars); System.out.println(s.length()); //it returns 3.
- 150. Special String Operations String Concatenation String Concatenation with Other Data Types String Conversion and toString( ) Character Extraction charAt( ) getChars( ) getBytes( ) toCharArray( ) String Comparison equals( ) and equalsIgnoreCase( ) regionMatches( ), startsWith( ) and endsWith( ) equals( ) Versus == compareTo( ) Searching Strings Modifying a String substring( ) concat( ) replace( ) trim( ) Changing the Case of Characters Within a String
- 151. Special String Operations String Concatenation String age = "9"; String s = "He is " + age + " years old."; System.out.println(s); // He is 9 years old. String Concatenation with Other Data Types int age = 9; String s = "He is " + age + " years old."; System.out.println(s); // He is 9 years old. String s = "four: " + 2 + 2; System.out.println(s); //This fragment displays four: 22 rather than the four: 4 String s = "four: " + (2 + 2); //Now s contains the string “four: 4”.
- 152. Special String Operations String Conversion using toString( ) // Override toString() for Box class. class Box { double width; double height; double depth; Box(double w, double h, double d) { width = w; height = h; depth = d; } public String toString() { return "Dimensions are " + width + " by " +depth + " by " + height + "."; } } class toStringDemo { public static void main(String args[]) { Box b = new Box(10, 12, 14); String s = "Box b: " + b; // concatenate Box object System.out.println(b); // convert Box to string System.out.println(s); } } The output of this program is shown here: Dimensions are 10.0 by 14.0 by 12.0 Box b: Dimensions are 10.0 by 14.0 by 12.0 Box’s toString() method is automatically invoked when a Box object is used in a concatenation expression or in a call to println( ).
- 153. Character Extraction char charAt(int where) //To extract a single character from a String char ch; ch = "abc".charAt(1); //assigns the value “b” to ch. void getChars(int sourceStart, int sourceEnd, char target[ ], int targetStart) //to extract more than one character at a time. byte[ ] getBytes( ) //to store the characters in an array of bytes and it uses the default character-to-byte conversions provided by the platform. //String source=“hi”+”how”+”are”+”you.” //byte buf[] = source.getBytes(); char[ ] toCharArray( ) //to convert all the characters in a String object into a character array. It returns an array of characters for the entire string. class getCharsDemo { public static void main(String args[]) { String s = "This is a demo of the getChars method."; int start = 10; int end = 14; char buf[] = new char[end - start]; s.getChars(start, end, buf, 0); System.out.println (buf); } } Here is the output of this program: demo
- 154. class GetBytesDemo{ public static void main(String[] args){ String str = "abc” + “ABC”; byte[] b = str.getBytes(); //char[] c=str.toCharArray(); System.out.println(str); for(int i=0;i<b.length;i++){ System.out.print(b[i]+" "); //System.out.print(c[i]+" "); } } } Output: 97 98 99 65 66 67 //a b c A B C
- 155. String Comparison boolean equals(Object str) //To compare two strings for equality. It returns true if the strings contain the same characters in the same order, and false otherwise. boolean equalsIgnoreCase(String str) //To perform a comparison that ignores case differences. // Demonstrate equals() and equalsIgnoreCase(). class equalsDemo { public static void main(String args[]) { String s1 = "Hello"; String s2 = "Hello"; String s3 = "Good-bye"; String s4 = "HELLO"; System.out.println(s1.equals(s2)); System.out.println(s1.equals(s3)); System.out.println(s1.equals(s4)); System.out.println(s1.equalsIgnoreCase(s4)); } } The output from the program is shown here: true false false true
- 156. String Comparison boolean regionMatches(int startIndex, String str2, int str2StartIndex, int numChars) boolean regionMatches(boolean ignoreCase, int startIndex, String str2, int str2StartIndex, int numChars) //The regionMatches( ) method compares a specific region inside a string with another specific region in another string. //startIndex specifies the index at which the region begins within the invoking String object. //The String being compared is specified by str2. The index at which the comparison will start within str2 is specified by str2StartIndex. //The length of the substring being compared is passed in numChars.
- 157. class RegionTest{ public static void main(String args[]){ String str1 = "This is Test"; String str2 = “THIS IS TEST"; if(str1.regionMatches(5,str2,5,3)) { // Case, pos1,secdString,pos1,len System.out.println("Strings are Equal"); } else{ System.out.println("Strings are NOT Equal"); } } } Output: Strings are NOT Equal String Comparison
- 158. boolean startsWith(String str) //to determine whether a given String begins with a specified string. boolean endsWith(String str) // to determine whether the String in question ends with a specified string. Ex: "Football".endsWith("ball") and "Football".startsWith("Foot") are both true. boolean startsWith(String str, int startIndex) //to specifies the index into the invoking string at which point the search will begin. Ex: "Football".startsWith("ball", 4) returns true. equals( ) Versus == // It compares the characters inside a String object //To compare two object references to see whether they refer to the same instance. String Comparison
- 159. // equals() vs == class EqualsNotEqualTo { public static void main(String args[]) { String s1 = "Hello"; String s2 = new String(s1); //String s2 = s1; System.out.println(s1.equals(s2)); System.out.println( s1 == s2); } } Output: true false String Comparison
- 160. int compareTo(String str) Value Meaning Less than zero The invoking string is less than str. Greater than zero The invoking string is greater than str. Zero The two strings are equal. int compareToIgnoreCase(String str) String Comparison
- 161. class SortString { static String arr[] = { "Now", "is", "the", "time", "for", "all", "good", "men", "to", "come", "to", "the", "aid", "of", "their", "country“}; public static void main(String args[]) { for(int j = 0; j < arr.length; j++) { for(int i = j + 1; i < arr.length; i++) { if(arr[i].compareTo(arr[j]) < 0) { String t = arr[j]; arr[j] = arr[i]; arr[i] = t; } } System.out.println(arr[j]); } } } The output of this program is the list of words: Now aid all come country for good is men of the the their time to to String Comparison
- 162. indexOf( ) //Searches for the first occurrence of a character or substring. lastIndexOf( ) //Searches for the last occurrence of a character or substring. int indexOf(int ch) //To search for the first occurrence of a character. int lastIndexOf(int ch) //To search for the last occurrence of a character. int indexOf(String str) //To search for the first or last occurrence of a substring. int lastIndexOf(String str) int indexOf(int ch, int startIndex) int lastIndexOf(int ch, int startIndex) int indexOf(String str, int startIndex) int lastIndexOf(String str, int startIndex) In all cases, the methods return the index at which the character or substring was found, or –1 on failure. Searching Strings
- 163. // Demonstrate indexOf() and lastIndexOf(). class indexOfDemo { public static void main(String args[]) { String s = "Now is the time for all good men " +"to come to the aid of their country."; System.out.println(s); System.out.println("indexOf(t) = " +s.indexOf('t')); System.out.println("lastIndexOf(t) = " +s.lastIndexOf('t')); System.out.println("indexOf(the) = " +s.indexOf("the")); System.out.println("lastIndexOf(the) = " +s.lastIndexOf("the")); System.out.println("indexOf(t, 10) = " +s.indexOf('t', 10)); System.out.println("lastIndexOf(t, 60) = " +s.lastIndexOf('t', 60)); System.out.println("indexOf(the, 10) = " +s.indexOf("the", 10)); System.out.println("lastIndexOf(the, 60) = " +s.lastIndexOf("the", 60)); } } Here is the output of this program: Now is the time for all good men to come to the aid of their country. indexOf(t) = 7 lastIndexOf(t) = 65 indexOf(the) = 7 lastIndexOf(the) = 55 indexOf(t, 10) = 11 lastIndexOf(t, 60) = 55 indexOf(the, 10) = 44 lastIndexOf(the, 60) = 55
- 164. // Substring replacement. class StringReplace { public static void main(String args[]) { String org = "This is a test. This is, too."; String result = org.substring(0, 2); System.out.println(result); } } Output: Th Modifying a String String substring(int startIndex) //To extract a substring, startIndex specifies the beginning index String substring(int startIndex, int endIndex) // Here endIndex specifies the stopping point. //endIndex-1
- 165. String concat(String str) //To concatenate two strings, concat( ) performs the same function as +. String s1 = "one"; String s2 = s1.concat("two"); String s1 = "one"; String s2 = s1 + "two"; String replace(char original, char replacement) //To replace all occurrences of one character in the invoking string with another character String s = "Hello".replace('l', 'w'); puts the string “Hewwo” into s. String trim( ) //Removes leading and trailing whitespaces. Here is an example: String s = " Hello World ".trim(); //This puts the string “Hello World” into s.
- 166. Data Conversion Using valueOf( ) static String valueOf(double num) // converts data from its internal format into a human-readable form. static String valueOf(long num) //each type can be converted properly into a string static String valueOf(Object ob) static String valueOf(char chars[ ])
- 167. Changing the Case of Characters Within a String String toLowerCase( ) //converts all the characters in a string from uppercase to lowercase. String toUpperCase( ) //converts all the characters in a string from lowercase to uppercase // Demonstrate toUpperCase() and toLowerCase(). class ChangeCase { public static void main(String args[]){ String s = "This is a test."; System.out.println("Original: " + s); String upper = s.toUpperCase(); String lower = s.toLowerCase(); System.out.println("Uppercase: " + upper); System.out.println("Lowercase: " + lower); } } Output: Original: This is a test. Uppercase: THIS IS A TEST. Lowercase: this is a test.
- 168. StringBuffer
- 169. StringBuffer( ) // The default constructor (the one with no parameters) reserves room for 16 characters without reallocation. StringBuffer(int size) // accepts an integer argument that explicitly sets the size of the buffer. StringBuffer(String str) // str + reserves room for 16 more characters without reallocation. StringBuffer Constructors
- 170. Methods length( ) and capacity( ) setLength( ) charAt( ) and setCharAt( ) getChars( ) append( ) insert( ) reverse( ) delete( ) and deleteCharAt( ) replace( ) substring( )
- 171. // StringBuffer length vs. capacity. class StringBufferDemo { public static void main(String args[]) { StringBuffer sb = new StringBuffer("Hello"); System.out.println("buffer = " + sb); System.out.println("length = " + sb.length()); System.out.println("capacity = " + sb.capacity()); } } Output: buffer = Hello length = 5 capacity = 21 int length( ) //The current length of a StringBuffer can be found via the length( ) method int capacity( ) //The total allocated capacity can be found through the capacity( ) method.
- 172. // Demonstrate charAt() and setCharAt(). class setCharAtDemo { public static void main(String args[]) { StringBuffer sb = new StringBuffer("Hello"); System.out.println("buffer before = " + sb); System.out.println("charAt(1) before = " + sb.charAt(1)); sb.setCharAt(1, 'i'); sb.setLength(2); System.out.println("buffer after = " + sb); System.out.println("charAt(1) after = " + sb.charAt(1)); } } void setLength(int len) //To set the length of the buffer within a StringBuffer object. char charAt(int where) //The value of a single character can be obtained from a StringBuffer via the charAt( ) method. void setCharAt(int where, char ch) //To set the value of a character, ch specifies the new value of that character. Output: buffer before = Hello charAt(1) before = e buffer after = Hi charAt(1) after = i
- 173. void getChars(int sourceStart, int sourceEnd, char target[ ], int targetStart) // To copy a substring of a StringBuffer into an array StringBuffer append(String str) // concatenates the string representation of any other type of data to the end of the invoking StringBuffer object. StringBuffer append(int num) StringBuffer append(Object obj) String.valueOf( ) is called for each parameter to obtain its string representation. The result is appended to the current StringBuffer object.
- 174. // Demonstrate append(). class appendDemo { public static void main(String args[]) { String s; int a = 42; StringBuffer sb = new StringBuffer(40); s = sb.append("a = ").append(a).append("!").toString(); System.out.println(s); } } Output: a = 42!
- 175. //The insert( ) method inserts one string into another. StringBuffer insert(int index, String str) StringBuffer insert(int index, char ch) StringBuffer insert(int index, Object obj) // Demonstrate insert(). class insertDemo { public static void main(String args[]) { StringBuffer sb = new StringBuffer("I Java!"); sb.insert(2, "like "); System.out.println(sb); } } Output: I like Java!
- 176. StringBuffer reverse( ) // reverse the characters within a StringBuffer object using reverse( ) // Using reverse() to reverse a StringBuffer. class ReverseDemo { public static void main(String args[]) { StringBuffer s = new StringBuffer("abcdef"); System.out.println(s); s.reverse(); System.out.println(s); } } Output: abcdef fedcba
- 177. StringBuffer delete(int startIndex, int endIndex) // to delete characters. StringBuffer deleteCharAt(int loc) // Demonstrate delete() and deleteCharAt() class deleteDemo { public static void main(String args[]) { StringBuffer sb = new StringBuffer("This is a test."); sb.delete(4, 7); System.out.println("After delete: " + sb); sb.deleteCharAt(0); System.out.println("After deleteCharAt: " + sb); } } Output: After delete: This a test. After deleteCharAt: his a test.
- 178. StringBuffer replace(int startIndex, int endIndex, String str); //It replaces one set of characters with another set inside a StringBuffer object. // The replacement string is passed in str. // Demonstrate replace() class replaceDemo { public static void main(String args[]) { StringBuffer sb = new StringBuffer("This is a test."); sb.replace(5, 7, "was"); System.out.println("After replace: " + sb); } } Output: After replace: This was a test. String substring(int startIndex) //to return sub strings. String substring(int startIndex, int endIndex)
- 179. The StringTokenizer class provides the first step in parsing process, often called the lexer (lexical analyzer) or scanner. Parsing is the division of text into a set of discrete parts, or tokens. To use StringTokenizer Specify an input string and a delimiter string. Delimiters are characters that separate tokens. Each character in the delimiters string is considered a valid delimiter. Ex: “ , ; : a” The default set of delimiters consists of the whitespace characters: Ex: space, tab, newline. StringTokenizer
- 180. StringTokenizer Constructors StringTokenizer(String str) StringTokenizer(String str, String delimiters) StringTokenizer(String str, String delimiters, boolean delimAsToken) Methods int countTokens( ) //returns number of tokens in the string. boolean hasMoreTokens( ) //checks whether tokens are there or not String nextToken( )//returns the token in the string
- 181. // Demonstrate StringTokenizer. import java.util.StringTokenizer; class STDemo{ //static String str = "Hello Welcome to Java Programming"; static String str = "Hello,Welcome,to,Java,Programming"; public static void main(String args[]) { //StringTokenizer st = new StringTokenizer(str); //StringTokenizer st = new StringTokenizer(str,","); StringTokenizer st = new StringTokenizer(str,",",true); while(st.hasMoreTokens()) { String tokens = st.nextToken(); System.out.println(tokens + "n"); } } } Output: Hello , Welcome , to , Java , Programming
- 182. Exercise1: Write a java program that reads a line of integers and then displays each integer and find the sum of the integers (using StringTokenizer)
- 183. import java.util.Scanner; import java.util.*; class Token{ static int sum=0; public static void main(String sree[]){ Scanner s=new Scanner(System.in); System.out.print("Enter sum of integers: "); String str=s.next(); StringTokenizer st=new StringTokenizer(str,"+"); while(st.hasMoreTokens()){ sum=sum+Integer.parseInt(st.nextToken()); } System.out.println("Sum of "+str+“is: "+sum); } } Output: Enter sum of integers: 10+20+30+40 Sum of 10+20+30+40 is: 100