Initialize an Empty Array in Java

  1. new Keyword to Declare an Empty Array in Java
  2. Declare of an Empty Array Using new Keyword With Predefined Size
  3. Initialize an Array Without Using new Keyword

This tutorial article will introduce how to initialize an empty array in Java.

There are several ways to declare an array in Java, but we can only do this dynamically.

new Keyword to Declare an Empty Array in Java

The new keyword initiates an object dynamically (runtime allocation of memory), and returns the reference of that object’s memory.

To declare an empty array in Java, we can use the new keyword. After the declaration of an empty array, we can initialize it using different ways.

The syntax of declaring an empty array is as follows.

data-type[] array-name = new data-type[size];
//or
data-type array-name[] = new data-type[size];

There are two major ways to declare an empty array in Java using the new keyword that is as follows.

Declare of an Empty Array Using new Keyword With Predefined Size

We can declare an empty array using the new keyword with a predefined size. In this case, we will provide the size to the array before runtime, and then the array will be declared according to the size.

The example code of the declaration of an empty array by predefined size in Java and then initialize that array’s values are as follows.

public class Declare_Empty_Array {
    public static void main(String args[]) {
        int Size = 5;
        int array[] =new int[Size];
        for(int i=0;i<Size;i++)
        {
            array[i] = i+1;
            System.out.println("The value stored in array on index "+i+" is: "+array[i]);
        }
    }
}

In this above code, we declare an empty array with a predefined size and then initialize that array’s values using the for loop. We can also use the while loop for the same purpose.

The output of the code is as follows.

The value stored in the array on index 0 is: 1
The value stored in the array on index 1 is: 2
The value stored in the array on index 2 is: 3
The value stored in the array on index 3 is: 4
The value stored in the array on index 4 is: 5

Initialize an Array Without Using new Keyword

There is another way to initialize an array and then update its values without using the new keyword. In this method, we can initialize the array with predefined values and update them with our desired values.

import java.util.Scanner;
public class Declare_Empty_Array {
    public static void main(String args[]) {
        int array[] = {5, 5, 5, 5, 5};
        for(int i=0;i<array.length;i++)
        {
            array[i] = i+1;
            System.out.println("The value updated in array on index "+i+" is: "+array[i]);
        }
    }
}

In the above code, we initialize an array that has 5 stored in it initially, and after that, we can update its values.

The output of the code is as follows.

The value updated in array on index 0 is: 1
The value updated in array on index 1 is: 2
The value updated in array on index 2 is: 3
The value updated in array on index 3 is: 4
The value updated in array on index 4 is: 5

Related Article - Java Array

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