Can this class run fast than Hotspot ?

Question

My case in Sun hotspot is almost 2 times fast than jRockit. It's very strange.
package com.telegram;
public class byteutils {
     public final static byte[] bytea = { 48, 49, 50, 51, 52, 53, 54, 56, 57,
               58, 65, 66, 67, 68, 69, 70 };
     public byteutils() {
          super();
     * convert length = 2L letters Hexadecimal String to length = L bytes
     * Examples: [01][23][45][67][89][AB][CD][EF]
     public static byte[] convertBytes(String hexStr) {
          byte[] a = null;
          try {
               a = hexStr.getBytes("ASCII");
          } catch (java.io.UnsupportedEncodingException e) {
               e.printStackTrace();
          final int len = a.length / 2;
          byte[] b = new byte[len];
          int idx = 0;
          int h = 0;
          int l = 0;
          for (int i = 0; i < len; i++) {
               h = a[idx++];
               l = a[idx++];
               h = (h < 65) ? (h - 48) : (h - 55);
               l = (l < 65) ? (l - 48) : (l - 55);
               // if ((h < 0) || (l < 0)) return null;
               b[i] = (byte) ((h << 4) | l);
          a = null;
          return b;
     public static String convertHex(byte[] arr_b) {
          if (arr_b == null)
               return null;
          final int len = arr_b.length;
          byte[] byteArray = new byte[len * 2];
          int idx = 0;
          int h = 0;
          int l = 0;
          int v = 0;
          for (int i = 0; i < len; i++) {
               v = arr_b[i] & 0xff;
               l = v & 0xf;
               h = v >> 4;
               byteArray[idx++] = bytea[h];
               byteArray[idx++] = bytea[l];
          String r = null;
          try {
               r = new String(byteArray, "ASCII");
          } catch (java.io.UnsupportedEncodingException e) {
               e.printStackTrace();
          } finally {
               byteArray = null;
          return r;
     public static void main(String[] argv) {
          byte[] a = new byte[0x10000];
          for (int c = 0; c < 0x10000; c++) {
               a[c] = (byte) (c % 256);
          String s = "";
          int LOOP = 10000;
          long l = System.currentTimeMillis();
          for (int i = 0; i < LOOP; i++) {
               s = convertHex(a);
               a = convertBytes(s);
          l = System.currentTimeMillis() - l;
          double d = l / (double) LOOP;
          System.out.println("" + d + "ms.");
}

Answer 1

Thanks! Your code is essentially a microbenchmark testing the performance of sun.nio.cs.US_ASCII.Decoder.decodeLoop() and encodeLoop(), with ~35% and ~30% spent in those two methods respectively. I have verified the behavior (i.e. Sun is faster than JRockit). Due to the microbenchmark nature, it may not affect a larger running program, but it may merit a closer look regardless. I have forwarded to the JRockit perf team for analysis.
-- Henrik