System arraycopy() method in java

public static void arraycopy(Object source_arr, int sourcePos,
                            Object dest_arr, int destPos, int len)
Parameters : 
source_arr : array to be copied from
sourcePos : starting position in source array from where to copy
dest_arr : array to be copied in
destPos : starting position in destination array, where to copy in
len : total no. of components to be copied.

public class ArrayCopyDemo
{
   public static void main(String[] args)
   {
      int[] arrOne = {2,4,6,8,10,12,14,16,18,20};
      int[] arrTwo = {1,3,5,7,9,11,13,15,17,19};
      int[] sourceArr, sourcePosition, destinationArr[], destinationPosition, len;
      sourceArr = arrOne;
      sourcePosition = 2;
      destinationArr = arrTwo;
      destinationPosition = 5;
      len = 4;
      // printing elements of source array
      System.out.println("Source array : ");
      for(int a = 0; a < arrOne.length; a++)
         System.out.print(arrOne[a] + " ");
      System.out.println("");
      System.out.println("sourcePosition : " + sourcePosition);
      // print elements of destination array
      System.out.println("Destination array : ");
      for(int a = 0; a < arrTwo.length; a++)
         System.out.print(arrTwo[a] + " ");
      System.out.println("");
      System.out.println("destinationPosition : " + destinationPosition);
      System.out.println("Length : " + len);
      // system.arraycopy method in java
      System.arraycopy(sourceArr, sourcePosition, destinationArr, destinationPosition, len);
      // printing final array
      System.out.println("Final array : ");
      for(int a = 0; a < arrTwo.length; a++)
         System.out.print(arrTwo[a] + " ");
   }
}