用StopWatch 统计代码耗时

StopWatch sw = new StopWatch();
      sw.start();
      // long task simulation
      try {
          Thread.sleep(1000);
      } catch (Exception e) {
          e.printStackTrace();
      }
      sw.stop();
      System.out.println(sw.getTotalTimeMillis());

 StopWatch sw = new StopWatch();
      sw.start("A");
      Thread.sleep(500);
      sw.stop();
      sw.start("B");
      Thread.sleep(300);
      sw.stop();
      sw.start("C");
      Thread.sleep(200);
      sw.stop();
      System.out.println(sw.prettyPrint());