Clone a 2D array (matrix) in Java using Stream API

This post will discuss how to clone a 2D array (matrix) in Java using Stream API, whose column size may or may not be fixed.

1. Using `clone()` method

Since Java 8, you can use the streams API to clone a 2-dimensional array in Java. The following solution uses method reference int[]::clone for cloning, which behaves the same as using the lambda expression arr -> arr.clone().

import java.util.Arrays;

public class Main {

public static int[][] clone(int[][] mat) {

if (mat == null) {

return null;

}

return Arrays.stream(mat)

.map(int[]::clone) // or use .map(arr -> arr.clone())

.toArray(int[][]::new);

}

public static void main(String[] args) {

int[][] mat = new int[][] {

{3, 5, 7, 9},

{2, 4, 6},

{10, 12}

};

int[][] copy = clone(mat);

Arrays.stream(copy).map(Arrays::toString).forEach(System.out::println);

}

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Output:

[3, 5, 7, 9]
[2, 4, 6]
[10, 12]

2. Using `Arrays.copyOf()` method

Another alternative is to use the Arrays.copyOf() method to create a complete copy of a single-dimensional array. We can use Stream API .map() method to clone a 2-dimensional array, as demonstrated below: