Java StopWatch挂起和恢复计时器不起作用

以下代码的目的是测试StopWatch的复位，启动，挂起和恢复。应该有可能在给定的时间点暂停秒表，然后再恢复。在这种情况下，经过时间是当计时器最终停止时所有暂停和恢复事件的累积总数。如果我删除了timer.suspend（）和timer.resume（），代码可以正常工作。当我运行代码时，线程进入睡眠状态达2.3秒，并在输出中给出经过的时间2300。但是，使用suspend and resume方法，它将休眠2.3秒，但输出为0。

您能建议/建议代码中有什么问题吗？

谢谢你。

 interface StopWatch {

public void reset();
public void start();
public void stop();
public void suspend();
public void resume();
public long getElapsedTime();
public int getState();
public static final int RESET = 0, RUNNING =1, STOPPED =2, SUSPENDED = 3, RESUME = 0;}

计时器类

class Timer implements StopWatch{
private long startTime;
private long elaspedTime;
private int state;
public Timer(){reset();}

public void reset(){
    state = RESET;
    elaspedTime = 0;
}
public void start(){
    if(state==RESET){
        startTime = System.currentTimeMillis();
        state = RUNNING;
        }
}     

公共无效stop（）{

    if(state == RUNNING){
        elaspedTime = System.currentTimeMillis() - startTime;
        state = STOPPED;
    }
}
public void suspend() {
    if(state == RUNNING){
        elaspedTime = System.currentTimeMillis() - startTime;
        state = SUSPENDED;
    }
}
public void resume(){

    if(state == RUNNING){
        elaspedTime = System.currentTimeMillis() - startTime;
        state = RESUME;
    }
}

public long getElapsedTime() {
    if(state == RUNNING){
        long elasped = System.currentTimeMillis() - startTime;
        return elasped;
    }
    else if (state == STOPPED)
        return elaspedTime;

    else if (state == RESUME)
        return elaspedTime;
    return 0;
}
public int getState(){
    return state;
}}

秒表测试

 public class StopWatchTest {
        public static  void main (String[] args){
        Timer timer = new Timer();
        timer.start();
        try{
            Thread.sleep(2300);
            timer.suspend();
            timer.resume();
        }catch (InterruptedException e){}
        timer.stop();
        long duration = timer.getElapsedTime();
        System.out.println(duration);
    }}