Arrays copyOf() in Java with examples

java.util.Arrays.copyOf() method is in java.util.Arrays class. It copies the specified array, truncating or padding with false (if necessary) so the copy has the specified length. 

Syntax:

 copyOf(int[] original, int newLength) 

• original – original array
• newLength – copy of an original array

Java

// Java program to illustrate copyof method
import java.util.Arrays;

public class Main
{
    public static void main(String args[])
    {
        // initializing an array original
        int[] org = new int[] {1, 2 ,3};

        System.out.println("Original Array");
        for (int i = 0; i < org.length; i++)
            System.out.print(org[i] + " ");

        // copying array org to copy
        int[] copy = Arrays.copyOf(org, 5);

        // Changing some elements of copy
        copy[3] = 11;
        copy[4] = 55;

        System.out.println("\nNew array copy after modifications:");
        for (int i = 0; i < copy.length; i++)
            System.out.print(copy[i] + " ");
    }
}

Output

Original Array
1 2 3 
New array copy after modifications:
1 2 3 11 55 

What happens if the length of a copied array is greater than the original array? The two arrays will have same values for all the indices that are valid in original array and new array. However, the indices missing in original will have zero in copy in case the copied array length is more than the original array. 

Java

// Java program to illustrate copyOf when new array
// is of higher length.
import java.util.Arrays;

public class Main
{
public static void main(String args[])
{
    // initializing an array original
    int[] org = new int[] {1, 2 ,3};

    System.out.println("Original Array :");
    for (int i = 0; i < org.length; i++)
        System.out.print(org[i] + " ");

    // copying array org to copy
    // Here, new array has 5 elements - two
    // elements more than the original array
    int[] copy = Arrays.copyOf(org, 5);

    System.out.print("\nNew array copy (of higher length):\n");
    for (int i = 0; i < copy.length; i++)
        System.out.print(copy[i] + " ");
    }
}

Output

Original Array :
1 2 3 
New array copy (of higher length):
1 2 3 0 0 

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