How to Copy Array in Java: Syntax and Examples

In Java, you can copy an array using System.arraycopy(), Arrays.copyOf(), or the array's clone() method. These methods create a new array with the same elements as the original.

Syntax

Here are common ways to copy an array in Java:

• System.arraycopy(src, srcPos, dest, destPos, length): Copies elements from src starting at srcPos to dest starting at destPos for length elements.
• Arrays.copyOf(original, newLength): Returns a new array copying the first newLength elements from original.
• array.clone(): Creates a new array that is a shallow copy of array.

java

System.arraycopy(sourceArray, 0, destinationArray, 0, sourceArray.length);

int[] newArray = java.util.Arrays.copyOf(originalArray, originalArray.length);

int[] clonedArray = originalArray.clone();

Example

This example shows how to copy an integer array using the three common methods and prints the copied arrays.

java

import java.util.Arrays;

public class ArrayCopyExample {
    public static void main(String[] args) {
        int[] original = {1, 2, 3, 4, 5};

        // Using System.arraycopy
        int[] copy1 = new int[original.length];
        System.arraycopy(original, 0, copy1, 0, original.length);

        // Using Arrays.copyOf
        int[] copy2 = Arrays.copyOf(original, original.length);

        // Using clone method
        int[] copy3 = original.clone();

        System.out.println("Copy using System.arraycopy: " + Arrays.toString(copy1));
        System.out.println("Copy using Arrays.copyOf: " + Arrays.toString(copy2));
        System.out.println("Copy using clone(): " + Arrays.toString(copy3));
    }
}

Output

Copy using System.arraycopy: [1, 2, 3, 4, 5]
Copy using Arrays.copyOf: [1, 2, 3, 4, 5]
Copy using clone(): [1, 2, 3, 4, 5]

Common Pitfalls

One common mistake is to assign one array to another using =, which copies only the reference, not the actual array. This means changes to one array affect the other.

Also, clone() and System.arraycopy() perform shallow copies, so if the array contains objects, only references are copied, not the objects themselves.

java

public class WrongCopy {
    public static void main(String[] args) {
        int[] original = {1, 2, 3};
        int[] wrongCopy = original; // This copies reference, not array

        wrongCopy[0] = 99;
        System.out.println("Original after change: " + java.util.Arrays.toString(original));

        // Correct way using clone
        int[] correctCopy = original.clone();
        correctCopy[0] = 100;
        System.out.println("Original after correct copy change: " + java.util.Arrays.toString(original));
    }
}

Output

Original after change: [99, 2, 3]
Original after correct copy change: [99, 2, 3]

Quick Reference

Method	Description	Notes
System.arraycopy()	Copies elements from source to destination array	Fast, requires destination array pre-allocated
Arrays.copyOf()	Creates new array copying specified length	Easy to use, returns new array
clone()	Creates shallow copy of the array	Simple, shallow copy only
Assignment (=)	Copies reference only, not array content	Avoid if you want independent copy

Key Takeaways

Use System.arraycopy, Arrays.copyOf, or clone() to copy arrays in Java.

Assignment copies only the reference, not the array content.

clone() and System.arraycopy() perform shallow copies for object arrays.

Arrays.copyOf returns a new array with specified length.

Always create a new array to avoid unexpected changes to the original.