Arrays in Java

Java arrays are not very different from other programming languages; only a little syntax and can vary. In this, arrays in the java article we will learn a small introduction of an array, what is the syntax of java arrays? and we will do some practical examples.

What is a Java array?

Arrays are an object which contains the similar type of data in a contiguous memory location. It is nothing but a data structure where we store similar elements. We can store only a fixed set of values in an array. Java arrays are index-based the first element’s position is stored at the 0th index, 2nd the one is stored on the 1st index and respectively. This function is different from c and c++.

Java array indexing example

Syntax:

We can declare a array in two ways:

1) data type [size] variable;
   Variable=new datatype[size];  

2) data type var-name[];
 variable = new datatype[];

Types of Array in java

In java, Two types of arrays are present, they are:

• Single dimensional array
• Multi-dimensional array

Single dimensional array

In the above snapshot, we have shown the indexing of a single dimension array.

Integer array Example:

public class ArrayExample {

	public static void main(String[] args) {
		 
        int value = 7;
        
        int[] values;
        values = new int[3];
        
        System.out.println(values[0]);
        
        values[0] = 1;
        values[1] = 2;
        values[2] = 3;
        
        System.out.println(values[0]);
        System.out.println(values[1]);
        System.out.println(values[2]);
        
        for(int i=0; i < values.length; i++) {
            System.out.println(values[i]);
        }
       
        int[] numbers = {5, 6, 7};
     
        for(int i=0; i < numbers.length; i++) {
            System.out.println(numbers[i]);
        }

	}

}

Output:

String array Example:

public class ArrayExample {

    public static void main(String[] args) {
        
        // Declare array of (references to) strings.
        String[] words = new String[3];
        
        // Set the array elements (point the references
        // at strings)
        words[0] = "Hello";
        words[1] = "to";
        words[2] = "you";
        
        // Access an array element and print it.
        System.out.println(words[2]);
        
        // Simultaneously declare and initialize an array of strings
        String[] fruits = {"apple", "banana", "pear", "kiwi"};
        
        // Iterate through an array
        for(String fruit: fruits) {
            System.out.println(fruit);
        }
}
}

Output:

you
apple
banana
pear
kiwi

Multi-Dimensional Arrays:

When we want to print a matrix or use rows and columns, we can use a multi-dimensional array. Simply we can that multi-dimensional array – data is stored in a row and column-based indexes.

public class ArrayExample {

	public static void main(String[] args) {
		 // 1D array
        int[] values = {3, 5, 2343};
        
        // Only need 1 index to access values.
        System.out.println(values[2]);
        
        // 2D array (grid or table)
        int[][] grid = {
            {3, 5, 2343},
            {2, 4},
            {1, 2, 3, 4}
        };
        
        // Need 2 indices to access values
        System.out.println(grid[1][1]);
        System.out.println(grid[0][2]);
        
        // Can also create without initializing.
        String[][] texts = new String[2][3];
        
        texts[0][1] = "Hello there";
        
        System.out.println(texts[0][1]);
        
        // How to iterate through 2D arrays.
        // first iterate through rows, then for each row
        // go through the columns.
        for(int row=0; row < grid.length; row++) {
            for(int col=0; col < grid[row].length; col++) {
                System.out.print(grid[row][col] + "\t");
            }
            
            System.out.println();
        }
        
        // The last array index is optional.
        String[][] words = new String[2][];
        
        // Each sub-array is null.
        System.out.println(words[0]);
        
        // We can create the subarrays 'manually'.
        words[0] = new String[3];
        
        // Can set a values in the sub-array we
        // just created.
        words[0][1] = "hi there";
        
        System.out.println(words[0][1]);
	}
}

Output:

All these examples are the examples of static array where we initialized the size of the array. After this we are showing the example of dynamic array.

import java.util.Scanner;

public class ArrayExample {

	public static void main(String[] args) {
		int i,size ;
		Scanner scanner= new Scanner(System.in);
		System.out.println("Enter the size of array: ");
		 size = scanner.nextInt();
		
		  int a[]=new int[10];
		  
		for(i=0; i<size; i++) {
			a[i]= scanner.nextInt();
		}
		System.out.print("Print array");
		for( i=0; i<size; i++) {
			System.out.println(a[i]);
		}
	}
	
}

Output:

0
1
2
3
4
5
6
7
8
9

Java ArrayList:

Arraylist is nothing but a class which uses a dynamic array to store the value. It has no size limit we can add remove the element anytime. It is present in the java.util package. It might be slower than a normal array but it can be helpful in programs where lots of manipulation in the array is needed. 

ArrayList class declaration

import java.util.ArrayList; // importing the ArrayList class

ArrayList<String> cars = new ArrayList<String>(); //Creating an ArrayList object called cars that is storing strings

This is small introduction of arraylist we will discuss it in separate post.

FAQs:

Must Read:

• Java Methods
• Java Break and Continue Statement