Core Java - SPLessons

Java Array

Chapter 27

SPLessons 5 Steps, 3 Clicks
5 Steps - 3 Clicks

Java Array

Java Array

shape Description

Java Array, Array is nothing but collection of similar data types and it can be also known as static data structure why because the size of an array will be given at the time of its declaration. Array starts from zero. Following is the syntax to declare an array.

datatype[] identifier;

shape Conceptual
Figure

Advantages and Disadvantages

shape Description


Array Types

shape Description

Java Array consist of two types as follows.

Single Dimensional Array

Following is the syntax to declare single dimensional array.

dataType[] arr;

Following is an example which describes more about the single dimensional array.
singledimentional.java

public class singledimentional {
	public static void main(String args[]){  
		  
		int a[]=new int[5];//declaration and instantiation  
		a[0]=100;//initialization  
		a[1]=200;  
		a[2]=870;  
		a[3]=640;  
		a[4]=850;  
		  
		//printing array  
		for(int i=0;i<a.length;i++)//length is the property of array  
		System.out.println(a[i]);  
		  
		}
}

Output
Now compile the code, result will be as follows.

100
200
870
640
850

Multi Dimensional Array

Following is the syntax to declare multi dimensional array.

dataType[][] arrayRefVar;

Following is an example which describes more about the multi dimensional array.
multidimensional.java

public class multidimensional {
	public static void main(String args[]){  
		  
		//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();  
		}  
		  
		}
}

Output
When compile the code, resutl will be as follows.

1 2 3 
2 4 5 
4 4 5 

Primitive Array and Derived Array

shape Primitive
Array

Primitive array is an array of primitive types. Primitive array is defined by using datatypes.
Ex:int[] array1=new int[5];
The following is an example for the primitive array.

package com.spl.primitive;

public class PrimitiveArray {
	public static void main(String[] args) {
		System.out.println("Program starts");
		int[] array1;//declaration
		array1=new int[5];//initialization
		System.out.println("Array value="+array1);
		System.out.println("Array length="+array1.length);
		System.out.println("2nd element="+array1[1]);
		System.out.println("Using normal for loop printing the values");
		for(int i=0;i<array1.length;i++)
		{
			System.out.println(i+"th element is"+array1[i]);
		}
		System.out.println("Using advanced for loop printing the values");
		for(int k:array1)
		{
			System.out.println("element is"+k);
		}
		System.out.println("Program ends");
		
	}
}

Output:

Program starts
Array value=[I@19eelac
Array length=5
2nd element=0
Using normal for loop printing the values
0th element is0
1th element is0
2th element is0
3th element is0
4th element is0
Using advanced for loop printing the values
element is0
element is0
element is0
element is0
element is0
Program ends

shape Derived
Array

Java Array of derived classes is known as derived array. This array is created by java types.
Ex: Apple[] array2=new Apple[5];
The following is an example for the Derived array.

package com.spl.primitive;

public class DerivedArray {
	public static void main(String[] args) {
		System.out.println("Program starts");
		//Array of Apple type
		Apple[] array1;//declaration
		array1=new Apple[5];
		//creating objects
		array1[0]=new Apple();
		array1[1]=new Apple();
		array1[2]=new Apple();
		array1[3]=new Apple();
		array1[4]=new Apple();
		//you can override toString() method in Apple Class
		System.out.println("array1 value="+array1);
		
		System.out.println("Using normal for loop printing the values");
		for(int i=0;i<array1.length;i++)
		{
			System.out.println(i+"th element is="+array1[i]);
		}
		System.out.println("Using advanced for loop printing the values");
		for(Apple k:array1)
		{
			System.out.println("element is="+k);
		}
		System.out.println("Program ends");
		
	}
}
class Apple
{
	
}

Output:

Program starts
array value1=[Lcom.spl.primitive.Apple;@ififba0
Using normal for loop printing the values
0th element is=com.spl.primitive.Apple@1befab0
1th element is=com.spl.primitive.Apple@13c5982
2th element is=com.spl.primitive.Apple@1186fab
3th element is=com.spl.primitive.Apple@14b7453
4th element is=com.spl.primitive.Apple@c21495
Using advanced for loop printing the values
element is=com.spl.primitive.Apple@1befab0
element is=com.spl.primitive.Apple@13c5982
element is=com.spl.primitive.Apple@1186fab
element is=com.spl.primitive.Apple@14b7453
element is=com.spl.primitive.Apple@c21495
Program ends

In derived array, an instance of the class can be stored.Suppose, if a derived array of type Apple is created, different types of Apple can be stored in that Java Array.


The following is an example for addition of 2 matrices in java.

package com;

public class ArrayAddition {
	public static void main(String args[]){  
		//creating two matrices  
		int a[][]={{2,3,4},{4,4,5}};  
		int b[][]={{1,5,4},{3,7,5}};  
		  
		//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  
		}  
		  
		}}  

Output:
The result will be as follows.

3 8 8 
7 11 10 

Summary

shape Key Points

  • The disadvantage of arrays can be overcome by using collection API’s or framework.
  • The limitation of array is, it is of homogeneous type and every element is referred through index only and elements are not stored in the structured format and array size is restricted.