![public static void main(String[] args)
• – is the starting point of every Java application. The parentheses after
the identifier main indicate that it’s a program building block called a
method. Java class declarations normally contain one or more
methods. For a Java application, one of the methods must be called
main and must be defined– Parenthesis used to indicate a function](https://image.slidesharecdn.com/lecture02java-210324171649/85/Lecture02-java-3-320.jpg)
![31
Symbol
( )
Name
Parentheses
Purpose
Used to contain list of
parameters
Used to maintain the
value of arrays
Used to declare array type
Terminates statements
Used to chain statements
together inside a for
statement
Used to separate package
{ } Braces
[ ]
;
,
Brackets
Semicolon
Comma
. Period
names and variables](https://image.slidesharecdn.com/lecture02java-210324171649/85/Lecture02-java-5-320.jpg)
![• Variables that score integer are declared as integer type
• Use int as the declaration of integer type
Public static void main(String[]args){
{
int x;
x = 1;
System.out.println( “x= ”+x);
}
Declare variable x as integer type
Assign integer 1 to variable x
Output the content of variable x
The variable name (identifier) can be arbitray but must start with alphabet.
Keywords of java language cannot be used as variable name.
= is assignment operator that assigns the expression in the right hand to the variable in the left hand
To declare variable, specify the type (int for integer type)
followed by the variable name.](https://image.slidesharecdn.com/lecture02java-210324171649/85/Lecture02-java-8-320.jpg)
![• What happens whe the following programs are compiled an executed?
Public class test{
Public static void main(String[]args){
{
x = 1;
System.out.println("x = “+x);
}
}
Public class test1{
Public static void main(String[]args){
{
int x;
System.out.println("x = “+x);
}
}
Variable x is not declared before
assigned a value. Compile error.
Variable declared but not assigned
a value might contain meaningless
value (garbage).
This would display nonsense value.](https://image.slidesharecdn.com/lecture02java-210324171649/85/Lecture02-java-10-320.jpg)
![Public class ahmad{
public static void main(String args[]) {
char ch1, ch2;
ch1=88; // code for X
ch2= ‘Y’;
System.out.print (“ch1 and ch2: ”);
System.out.println(ch1 + “ ” +ch2);
}
}](https://image.slidesharecdn.com/lecture02java-210324171649/85/Lecture02-java-11-320.jpg)
![Public class bool{
public static void main(String args[]) {
boolean b;
b = false;
System.out.println(“b is ” +b);
b=true;
System.out.println(“b is ” +b);
}
}](https://image.slidesharecdn.com/lecture02java-210324171649/85/Lecture02-java-12-320.jpg)
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Lecture02 java
- 1. Welcome To Computer Technology Institute (CTI) Programming Fundamentals Using java Lecture 2 Jawid Ahmad Niazi 1 Prepared By: Jawid Ahmad Niazi
- 2. Welcome to Java Programming! • Comments – Text surrounded by /* and */ or // is ignored by computer – Used to describe program • public class Welcome1 – Every Java program consists of at least one class that you define – Java is case sensitive—uppercase and lowercase letters are distinct—so value and Value are different identifiers
- 3. public static void main(String[] args) • – is the starting point of every Java application. The parentheses after the identifier main indicate that it’s a program building block called a method. Java class declarations normally contain one or more methods. For a Java application, one of the methods must be called main and must be defined– Parenthesis used to indicate a function
- 4. Welcome to Java Programming! The output of the program will be:
- 5. 31 Symbol ( ) Name Parentheses Purpose Used to contain list of parameters Used to maintain the value of arrays Used to declare array type Terminates statements Used to chain statements together inside a for statement Used to separate package { } Braces [ ] ; , Brackets Semicolon Comma . Period names and variables
- 6. • Integers – This group includes byte, short, int, long which are for whole valued signed numbers. • Floating-point numbers – This group includes float and double, which represent numbers with fractional precision. • Characters – This group includes char, which represents symbols in a character set, like letters and numbers. • Boolean – This group includes boolean, which is a special type for representing true/false values.
- 7. • To store value in program we use variable. • Each variable is categorized by type according to what type of value it stores. Integer, floating-point, and character are frequently used type. • Variables must be declared before use. Variable value Stored value is allocated somewhere in the computer memory. Novice programmer usually does not have to be conscious about the location. Variable is like a vessel that can store a value of a specified type
- 8. • Variables that score integer are declared as integer type • Use int as the declaration of integer type Public static void main(String[]args){ { int x; x = 1; System.out.println( “x= ”+x); } Declare variable x as integer type Assign integer 1 to variable x Output the content of variable x The variable name (identifier) can be arbitray but must start with alphabet. Keywords of java language cannot be used as variable name. = is assignment operator that assigns the expression in the right hand to the variable in the left hand To declare variable, specify the type (int for integer type) followed by the variable name.
- 9. Name Width in Bits double float 64 32
- 10. • What happens whe the following programs are compiled an executed? Public class test{ Public static void main(String[]args){ { x = 1; System.out.println("x = “+x); } } Public class test1{ Public static void main(String[]args){ { int x; System.out.println("x = “+x); } } Variable x is not declared before assigned a value. Compile error. Variable declared but not assigned a value might contain meaningless value (garbage). This would display nonsense value.
- 11. Public class ahmad{ public static void main(String args[]) { char ch1, ch2; ch1=88; // code for X ch2= ‘Y’; System.out.print (“ch1 and ch2: ”); System.out.println(ch1 + “ ” +ch2); } }
- 12. Public class bool{ public static void main(String args[]) { boolean b; b = false; System.out.println(“b is ” +b); b=true; System.out.println(“b is ” +b); } }
- 14. Any Question……