When copying the contents of one array into another, use the System.arraycopy method instead of an iterative loop. For example, consider the following arrays:

 	int[] first = {1, 2, 3};	int[] second = {4, 5, 6};	int[] third = new int[first.length + second.length];

One possible way of copying the contents of the first two arrays into the third one is to use loops, such as:

 	for (int i = 0; i < first.length; i++)		third[i] = first[i];	for (int i = 0; i < second.length; i++)		third[first.length + i] = second[i];

However, a better way of accomplishing the same task is to use the System.arraycopy method as in the following example:

 	System.arraycopy(first, 0, third, 0, first.length);	System.arraycopy(second, 0, third, first.length, second.length); 

Besides accomplishing the same result with less code, this approach has the added advantage of being faster, since arraycopy is implemented as a native method, and will generally execute faster than equivalent code written in Java. This advantage can be particularly significant with large arrays or where many arrays are being copied.