How to concatenate two arrays in Java

Question

I was working on two different arrays. But, now I want to concatenate these two arrays. How to do it?

Answer 1

To concatenate two arrays, we can use Apache library.

import org.apache.commons.lang.ArrayUtils;

public class ConcatenateArray {

    public static void main(String args[]) { 

        int [] first = {1,2,3, 4};

        int [] second = {5,6,7,8};

      

        // combine two arrays in Java using Apache commons ArrayUtils

        int [] combined = ArrayUtils.addAll(first, second);

     

        System.out.println("Concatenated array : " + Arrays.toString(combined));

      }
}

      

       

Answer 2

public <T> T[] concatenate(T[] a, T[] b) {
    int aLen = a.length;
    int bLen = b.length;

    @SuppressWarnings("unchecked")
    T[] c = (T[]) Array.newInstance(a.getClass().getComponentType(), aLen + bLen);
    System.arraycopy(a, 0, c, 0, aLen);
    System.arraycopy(b, 0, c, aLen, bLen);

    return c;
}

It will not work with primitive data type, it will work only with object type.