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How to initialize an array in Java

Educative Answers Team

An array is a collection of data objects of the same type. It is one of the fundamental data structures in Java and is incredibly useful for solving programming problems.

The values stored in the array are referred to as elements and each element is present at a particular index of the array.

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Declaring an array

The syntax for declaring an array is:

datatype[] arrayName;
  • datatype: The type of Objects that will be stored in the array eg. int, char etc.

  • [ ]: Specifies that the declared variable points to an array

  • arrayName: Specifies the name of the array

Initializing an array

Declaring an array does not initialize it. In order to store values in the array, we must initialize it first, the syntax of which is as follows:

datatype [ ] arrayName = new datatype [size];

There are a few different ways to initialize an array. Look at the following examples to get a better idea about array initialization.

1. Initializing an array without assigning values:

An array can be initialized to a particular size. In this case, the default value of each element is 0.

class HelloWorld {
    public static void main( String args[] ) {
        //Initializing array
        int[] array = new int[5];
        //Printing the elements of array
        for (int i =0;i < 5;i++)
        {
            System.out.println(array[i]);
        }
    }
}
Initializing elements of an array to zero

2. Initializing an array after a declaration:

An array can also be initialized after declaration.

class HelloWorld {
    public static void main( String args[] ) {
        //Array Declaration
        int[] array;
        //Array Initialization
        array = new int[]{1,2,3,4,5};
        //Printing the elements of array
        for (int i =0;i < 5;i++)
        {
            System.out.println(array[i]);
        }
    }
}

Note: When assigning an array to a declared variable, the new keyword must be used.

3. Initializing an array and assigning values:

An array can also be initialized during declaration.

class HelloWorld {
    public static void main( String args[] ) {
        int[] array = {11,12,13,14,15};
        //Printing the elements of array
        for (int i =0;i < 5;i++)
        {
            System.out.println(array[i]);
        }
    }
}

Note: When assigning values to an array during initialization, the size is not specified.

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array
java
initialization
data structures
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