Concatenate two Generic Arrays

import java.lang.reflect.Array;

public class ArrayUtils {

  @SuppressWarnings("unchecked")
  public static <T> T[] concatenate(T[] a, T[] b) {
    int len1 = a.length;
    int len2 = b.length;

    T[] c = (T[]) Array.newInstance(a.getClass().getComponentType(), len1 + len2);
    System.arraycopy(a, 0, c, 0, len1);
    System.arraycopy(b, 0, c, len1, len2);

    return c;
  }
}

public class TestArrayUtils {
  public static void main(String args[]) {
    Integer a[] = new Integer[10];
    Integer b[] = new Integer[10];

    for (int i = 0, j = 10; i < 10; i++, j--) {
      a[i] = i;
      b[i] = j;
    }

    printArray(a);
    printArray(b);
    printArray(ArrayUtils.concatenate(a, b));
  }

  static void printArray(Object obj[]) {
    for (Object tmp : obj)
      System.out.print(tmp + ",");
    System.out.println();
  }
}

Output

0,1,2,3,4,5,6,7,8,9,
10,9,8,7,6,5,4,3,2,1,
0,1,2,3,4,5,6,7,8,9,10,9,8,7,6,5,4,3,2,1,

public static void arraycopy(Object src, int srcPos, Object dest, int destPos, int length)

Copies an array from the specified source array, beginning at the specified position, to the specified position of the destination array.