Concatenate Two Arrays

 Concatenate Two Arrays using arraycopy

import java.util.Arrays;

public class Concat {

    public static void main(String[] args) {
        int[] array1 = {1, 2, 3};
        int[] array2 = {4, 5, 6};

        int aLen = array1.length;
        int bLen = array2.length;
        int[] result = new int[aLen + bLen];

        System.arraycopy(array1, 0, result, 0, aLen);
        System.arraycopy(array2, 0, result, aLen, bLen);

        System.out.println(Arrays.toString(result));
    }
}

Output

[1, 2, 3, 4, 5, 6]

In the above program, we’ve two integer arrays array1 and array2.

In order to combine (concatenate) two arrays, we find its length stored in aLen and bLen respectively. Then, we create a new integer array result with length aLen + bLen.

Now, in order to combine both, we copy each element in both arrays to result by using arraycopy() function.

The arraycopy(array1, 0, result, 0, aLen) function, in simple terms, tells the program to copy array1 starting from index 0 to result from index 0 to aLen.

Likewise, for arraycopy(array2, 0, result, aLen, bLen) tells the program to copy array2 starting from index 0 to result from index aLen to bLen.