Class System, making copies

February 15, 2002

Q: This question seems easy, but nonetheless I have no idea how to do it. I have a byte array: a[100] . Is there a simple way to copy only from a[0] to byte a[50] ? (I don't want to use a for/while loop.)

A: You're correct, the answer is really simple. The problem is that the answer lies in one of those classes everyone seems to overlook: java.lang.System. System includes the following method that does what you need:

public static void arraycopy(Object src,
                     int src_position,
                     Object dst,
                     int dst_position,
                     int length)

So, to copy your array, try the following:

byte [] dst = new byte[50];
System.arraycopy( a, 0, dst, 0, 50 );

Java developers also overlook the java.util.Arrays class. While Arrays won't help you with your copy problem, it will help you sort and fill your arrays.