问在编写共享资源之前获取WriteLock

EN

public class ScoreBoard {
private boolean scoreUpdated = false;
private int score = 0;
    String health = "Not Available";
final ReentrantReadWriteLock rrwl = new ReentrantReadWriteLock();
public String getMatchHealth() {
    rrwl.readLock().lock();
    if (scoreUpdated) {
        rrwl.readLock().unlock();
        rrwl.writeLock().lock();
        try {
          if (scoreUpdated) {
              score = fetchScore();
              scoreUpdated = false;
          }
          rrwl.readLock().lock();
        } finally {
          rrwl.writeLock().unlock(); 
        }   
    }   
    try {
         if (score % 2 == 0 ){
              health = "Bad Score";
          } else {
              health = "Good Score";
          }
    } finally {
          rrwl.readLock().unlock();
        }
    return health;
}
public void updateScore() {
    try {
        rrwl.writeLock().lock();
        //perform more task here
        scoreUpdated = true;
    }finally {
        rrwl.writeLock().unlock();
    }
}
private int fetchScore() {
    Calendar calender = Calendar.getInstance();
    return calender.get(Calendar.MILLISECOND);
}
}

public class ScoreUpdateThread implements Runnable {
private ScoreBoard scoreBoard;
public ScoreUpdateThread(ScoreBoard scoreTable) {
    this.scoreBoard = scoreTable;
}
@Override
public void run() {
    for(int i= 0; i < 5; i++) {
        System.out.println("Score Updated.");       
        scoreBoard.updateScore();
        try {
            Thread.sleep(2000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}
}

public class Main {
public static void main(String[] args) {
    final int threadCount = 2;
    final ExecutorService exService = Executors.newFixedThreadPool(threadCount);
    final ScoreBoard scoreBoard = new ScoreBoard();
    exService.execute(new ScoreUpdateThread(scoreBoard));
    exService.execute(new ScoreHealthThread(scoreBoard));           
    exService.shutdown();
}
}