我是一个学习mapreduce研究的学生。现在，我设计了一个mapreduce调度消息。我将实现算法。为了验证算法，我在原来的hadoop代码上添加了一些打印消息，例如jobtracker.java、fairscheduler.java等。。。但是，重新编译代码后，屏幕上不会显示打印消息。我无法验证我的算法的正确性。
例如，src/mapred/org/apache/hadoop/mapred/jobtracker.java中修改的代码如下所示。

...

public static JobTracker startTracker(JobConf conf
                                        ) throws IOException,
                                                 InterruptedException {       System.out.println("Hello! World!!!");
    return startTracker(conf, generateNewIdentifier());   }

  public static JobTracker startTracker(JobConf conf, String identifier)    throws IOException, InterruptedException {    System.out.println("Hello! World!!!");    return startTracker(conf, identifier, false);   }
     public static JobTracker startTracker(JobConf conf, String identifier, boolean initialize)    throws IOException, InterruptedException {     System.out.println("Hello! World!!!");    DefaultMetricsSystem.initialize("JobTracker");
    JobTracker result = null;
    while (true) {
        System.out.println("Hello! World!!!");
      try {
        result = new JobTracker(conf, identifier);
        result.taskScheduler.setTaskTrackerManager(result);
        break;
      } catch (VersionMismatch e) {
        throw e;
      } catch (BindException e) {
        throw e;
      } catch (UnknownHostException e) {
        throw e;
      } catch (AccessControlException ace) {
        // in case of jobtracker not having right access
        // bail out
        throw ace;
      } catch (IOException e) {
        LOG.warn("Error starting tracker: " + 
                 StringUtils.stringifyException(e));
      }
      Thread.sleep(1000);
    }
    if (result != null) {
        System.out.println("Hello! World!!!");
      JobEndNotifier.startNotifier();
      MBeans.register("JobTracker", "JobTrackerInfo", result);
      if(initialize == true) {
          System.out.println("Hello! World!!!");
        result.setSafeModeInternal(SafeModeAction.SAFEMODE_ENTER);
        result.initializeFilesystem();
        result.setSafeModeInternal(SafeModeAction.SAFEMODE_LEAVE);
        result.initialize();
      }
    }
    return result;   }

...

我编译了修改后的代码，并用以下命令替换了原来的hadoop：

cd $HADOOP_HOME
ant
mv build/hadoop-client-1.2.2-SNAPSHOT.jar hadoop-client-1.2.1.jar
mv build/hadoop-core-1.2.2-SNAPSHOT.jar hadoop-core-1.2.1.jar
mv build/hadoop-minicluster-1.2.2-SNAPSHOT.jar hadoop-minicluster-1.2.1.jar
mv build/hadoop-tools-1.2.2-SNAPSHOT.jar hadoop-tools-1.2.1.jar

然后，我启动了hadoop的新版本。它没有显示任何“你好！世界！！！”在我的显示器上留言。
如果你知道原因，请告诉我。在编译或执行时，是否需要添加一些参数？非常感谢你。