Array

1
Java Array
Handled By
Dr.T.Abirami
Associate Professor
Department of IT
Kongu Engineering College
Perundurai

Array
 used to store multiple values in a single
variable, instead of declaring separate
variables for each value.
 To declare an array, define the variable type
with square brackets []
 an array is a collection of similar types of
data.
 For example, if we want to store the names
of 100 people then we can create an array
of the string type that can store 100 names.
2

Types of Array in java
There are two types of array.
 Single Dimensional Array
 Multidimensional Array
3

Define an Array Variable in Java
Syntax:
datatype[] identifier; //preferred way
or
datatype identifier[];
Example:
char refVar[];
char[] refVar;
int[] refVar;
short[] refVar;
long[] refVar; 4

Initialize an array
 By using new operator array can be initialized
dataType[] arrayRefVar = new dataType[arraySize];
int[] age = new int[5]; //5 is the size of array.
int age[5]={22,25,30,32,35};
5

 String[] cars = {"Volvo", "BMW", "Ford",
"Mazda"};
 int[] myNum = {10, 20, 30, 40};
6

Access the Elements of an Array
 access an array element by referring to
the index number.
String[] cars = {"Volvo", "BMW", "Ford",
"Mazda"};
System.out.println(cars[0]);
// Outputs Volvo
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Array Length
"Mazda"};
System.out.println(cars.length);
// Outputs 4
8

Loop Through an Array
 the array elements with the for loop, and
use the length property to specify how
many times the loop should run.
"Mazda"};
for (int i = 0; i < 4; i++)
{
System.out.println(cars[i]);
}
9

//Java Program to illustrate the use of declaration, instantiation
//and initialization of Java array in a single line
class Testarray1{
public static void main(String args[]){
int a[]={33,3,4,5};//declaration, instantiation and initialization
//printing array
for(int i=0;i<a.length;i++)//length is the property of array
System.out.println(a[i]);
}}
10

Multidimensional Arrays
 containing one or more arrays.
 add each array within its own set of curly
braces:
dataType[][] arrayRefVar; (or)
dataType [][]arrayRefVar; (or)
dataType arrayRefVar[][]; (or)
dataType []arrayRefVar[];
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int[][] arr=new int[3][3];
//3 row and 3 column
arr[0][0]=1;
arr[0][1]=2;
arr[0][2]=3;
arr[1][0]=4;
arr[1][1]=5;
arr[1][2]=6;
arr[2][0]=7;
arr[2][1]=8;
arr[2][2]=9;
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class Testarray3{
//declaring and initializing 2D array
int arr[][]={{1,2,3},{2,4,5},{4,4,5}};
//printing 2D array
for(int i=0;i<3;i++){
for(int j=0;j<3;j++){
System.out.print(arr[i][j]+" ");
}
System.out.println();
}
}} 13

int[][] myNumbers = { {1, 2, 3, 4}, {5, 6, 7} };
int x = myNumbers[1][2];
System.out.println(x); // Outputs 7
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class Testarray5{
//creating two matrices
int a[][]={{1,3,4},{3,4,5}};
int b[][]={{1,3,4},{3,4,5}};
//creating another matrix to store the sum of two matrices
int c[][]=new int[2][3];
//adding and printing addition of 2 matrices
for(int i=0;i<2;i++){
for(int j=0;j<3;j++){
c[i][j]=a[i][j]+b[i][j];
System.out.print(c[i][j]+" ");
}
System.out.println();//new line
}
}}
15
addition of two matrices in Java

import java.util.Scanner;
class ExString
{
public static void main(String ar[])
{
int[] a=new int[2];
Scanner sc=new Scanner(System.in);
System.out.println("Enter the elements");
for(int i=0;i<2;i++)
{
a[i]=sc.nextInt();
}
System.out.println("Print the elements");
{
System.out.println(a[i]);
}
}
}
16

import java.util.Scanner;
class ExString
{
public static void main(String ar[])
{
int[][] a=new int[2][2];
Scanner sc=new Scanner(System.in);
System.out.println("Enter the elements");
{
for(int j=0;j<2;j++)
{
a[i][j]=sc.nextInt();
}
}
System.out.println("Print the elements");
{
for(int j=0;j<2;j++)
{
System.out.println(a[i][j]);
}
}
}
}
17

Jagged Array in Java
 arrays are of different size
 it is an array of arrays with different
number of columns.

Example
class Main
{
public static void main(String[] args)
{
// Declare a 2-D array with 3 rows
int myarray[][] = new int[3][];
// define and initialize jagged array
myarray[0] = new int[]{1,2,3};
myarray[1] = new int[]{4,5};
myarray[2] = new int[]{6,7,8,9,10};
// display the jagged array
System.out.println("Two dimensional Jagged Array:");
for (int i=0; i<myarray.length; i++)
{
for (int j=0; j<myarray[i].length; j++)
System.out.print(myarray[i][j] + " ");
System.out.println();
}
}
}
19

declaring a 2D array with different
columns
int arr[][] = new int[3][];
arr[0] = new int[3];
 int myarray[][] = new int[][]{
 new int[] { 1, 2, 3 };
 new int[] { 4, 5, 6, 7 };
 new int[] { 8, 9 };
 };

//initializing a jagged array
int count = 0;
for (int i=0; i<arr.length; i++)
for(int j=0; j<arr[i].length; j++)
arr[i][j] = count++;

differences between print() and
println().
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Sr.
No.
Key print() println()
1
Implementation print method is implemented
as it prints the text on the
console and the cursor remains
at the end of the text at the
console.
On the other hand, println method
is implemented as prints the text
on the console and the cursor
remains at the start of the next line
at the console and the next
printing takes place from next
line.
2
Nature The prints method simply print
text on the console and does
not add any new line.
While println adds new line after
print text on console.
3
Arguments print method works only with
input parameter passed
otherwise in case no argument
is passed it throws syntax
exception.
println method works both with
and without parameter and do
not throw any type of exception.

import java.io.*;
class JavaTester {
public static void main(String[] args){
System.out.print("Hello");
System.out.print("World");
}
}
23
Output
HelloWorld

import java.io.*;
class JavaTester {
public static void main(String[] args)
{
System.out.println("Hello");
System.out.println("World");
}
}
24
Output
Hello
World

Array

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