public static native void arraycopy(Object src, int srcPos,
Object dest, int destPos,
int length);/**
* Benchmarks System.arraycopy() vs. a for loop
* Expects as command line arguments paris of array size and
* number of repetitions of the benchmark.
*
* @author Michael Borgwardt
*/
public class CopyTest
{
static byte[] in;
static byte[] out;
public static void main(String[] args)
{
try
{
for(int n=0; n<args.length/2; n++)
{
int size = Integer.parseInt(args[n*2]);
int iterations = Integer.parseInt(args[n*2+1]);
in = new byte[size];
out = new byte[size];
long arraycopyTime = 0;
long loopcopyTime = 0;
long before = System.currentTimeMillis();
for(int i=0; i<iterations; i++)
{
System.arraycopy(in, 0, out, 0, size);
}
arraycopyTime = System.currentTimeMillis() - before;
before = System.currentTimeMillis();
for(int i=0; i<iterations; i++)
{
for(int j=0; j<in.length; j++)
{
out[j] = in[j];
}
}
loopcopyTime = System.currentTimeMillis() - before;
System.out.println("Array size: "+size+", Repetitions: "+iterations);
System.out.println("Loop: "+loopcopyTime +"ms, System.arrayCopy:"+arraycopyTime+"ms");
}
}
catch(Exception e)
{
e.printStackTrace();
}
}
}Wie man sieht ist die ArrayCopy insbesondere bei großen Arrays wesentlich performanter.
