每秒恒定“滴答声”（每秒线程）Java

Question

I know this may be completely obvious for more experenced programmers but I can't find anything on it.

I need to make a thread that "ticks" at a constant amount of times per second no matter how long the task it has to execute is. A task that takes longer than each tick would obviously not be possible and slow the number of ticks per second.

Thanks.

Answer 1

Use java.util.Timer.scheduleAtFixedRate :

 public void scheduleAtFixedRate(TimerTask task, Date firstTime, long period) 

Schedules the specified task for repeated fixed-rate execution , beginning at the specified time. Subsequent executions take place at approximately regular intervals, separated by the specified period.

In fixed-rate execution, each execution is scheduled relative to the scheduled execution time of the initial execution. If an execution is delayed for any reason (such as garbage collection or other background activity), two or more executions will occur in rapid succession to "catch up." In the long run, the frequency of execution will be exactly the reciprocal of the specified period (assuming the system clock underlying Object.wait(long) is accurate). As a consequence of the above, if the scheduled first time is in the past, then any "missed" executions will be scheduled for immediate "catch up" execution.

Fixed-rate execution is appropriate for recurring activities that are sensitive to absolute time, such as ringing a chime every hour on the hour, or running scheduled maintenance every day at a particular time. It is also appropriate for recurring activities where the total time to perform a fixed number of executions is important, such as a countdown timer that ticks once every second for ten seconds. Finally, fixed-rate execution is appropriate for scheduling multiple repeating timer tasks that must remain synchronized with respect to one another.

Answer 2

Here is a Thread version. A Timer would be the way to go but if you really want to use your own thread.

new Thread(new Runnable() {

    @Override
    public void run() {
        try {
        long before, sleepDuration, operationTime;
        for(int i=0;i<100;i++) {
            before = System.currentTimeMillis();
            // do your operations
            operationTime = (long)(1500*Math.random());
            System.out.print("Doing operations for "+operationTime+"ms\t");
            Thread.sleep(operationTime);

            // sleep for up to 1000ms
            sleepDuration = Math.min(1000, Math.max(1000 - (System.currentTimeMillis() - before), 0));
            Thread.sleep(sleepDuration);
            System.out.println("wait\t"+sleepDuration+"ms =\telapsed " + (operationTime+sleepDuration) + (operationTime > 1000 ? "<" : ""));
        }
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

}).start();

Answer 3

The Timer and TimerTask classes are perfect for your use.

Take a look at the docs http://docs.oracle.com/javase/6/docs/api/index.html?java/util/Timer.html or follow this lesson http://enos.itcollege.ee/~jpoial/docs/tutorial/essential/threads/timer.html

Let me know if I misunderstood your question.