Thread pool executes scheduled tasks

For scheduled tasks schedule Thread pool decision , So use Executors The scheduled tasks generated by the class are SchduledExecutorService Service implementation .

ScheduledExecutorService Is to implement the ExecutorService Interface

ScheduledExecutorService There are four ways

delay : Delay running for a few seconds TimeUnit : Time unit . 1000 millisecond = 1 second

Overloading methods schedule The only way to use the return value callable Interface . Sure scheduleFuture.get() Get the return value

function ：
Initial initialDelay cycle period.
if （ Delay time > The elapsed time ）
Initial time + Delay time
else {
Initial time + The elapsed time
}

function ： Initial time + The elapsed time + Delay time

test scheduleAtFixedRate() And scheduleWithFixedDelay（）

ScheduledExecutorService scheduledExecutorService = Executors.newSingleThreadScheduledExecutor();
        scheduledExecutorService.scheduleAtFixedRate(new Runnable() {
    
            @Override
            public void run() {
    
                SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd : hh:mm:ss");
                try {
    
                    sleep(6000);
                } catch (InterruptedException e) {
    
                    e.printStackTrace();
                }
                System.out.println(simpleDateFormat.format(new Date()));
            }
        }, 1000,5000, TimeUnit.MILLISECONDS);

ScheduledExecutorService scheduledExecutorService = Executors.newSingleThreadScheduledExecutor();
        scheduledExecutorService.scheduleWithFixedDelay(new Runnable() {
    
            @Override
            public void run() {
    
                SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd : hh:mm:ss");
                try {
    
                    sleep(6000);
                } catch (InterruptedException e) {
    
                    e.printStackTrace();
                }
                System.out.println(simpleDateFormat.format(new Date()));
            }
        }, 1000,5000, TimeUnit.MILLISECONDS);

summary ： If the thread execution time is greater than the interval , Therefore, the interval time will become the execution time . So we know that the thread runs in serial . and scheduleWithFixedDelay Is the default execution time + Execute thread after interval .