大家都说Timer不太好用，经常会遇到：如果前边的一个任务比较慢，超出了period,此时timer的下一次轮询也会延迟。
同事说ScheduleExecutorService可以避免该问题，我写个例子测试下：
package com.dx.testparallel; import java.util.concurrent.Executors; import java.util.concurrent.ScheduledExecutorService; import java.util.concurrent.TimeUnit;; public class TestTimer { public static void main(String[] args){ ScheduledExecutorService scheduledExecutorService=Executors.newScheduledThreadPool(1); //Creates and executes a periodic action that becomes enabled //first after the given initial delay, and subsequently with the //given period; that is executions will commence after //initialDelay then initialDelay+period, then initialDelay + 2 * //period, and so on. If any execution of the task encounters an //exception, subsequent executions are suppressed. //Otherwise, the task will only terminate via cancellation or //termination of the executor. If any execution of this task //takes longer than its period, then subsequent executions may //start late, but will not concurrently execute. scheduledExecutorService.scheduleAtFixedRate(new TheTask(), 0,1000, TimeUnit.MILLISECONDS); } }
package com.dx.testparallel; import java.sql.Timestamp; import java.text.SimpleDateFormat; import java.util.Date; import java.util.UUID; import javax.lang.model.element.VariableElement; public class TheTask implements Runnable{ @Override public void run() { Timestamp ts = new Timestamp(System.currentTimeMillis()); UUID uuid = UUID.randomUUID(); System.out.println("task"+uuid+" start:"+ts.toString()); // long num=0; // for(int a=0;a<100000;a++){ // for(int i=0;i<1000000;i++){ // for(int j=0;j<1000000;j++){ // num= a*i*j; // } // } // } try { Thread.sleep(2000); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } ts = new Timestamp(System.currentTimeMillis()); System.out.println("task"+uuid+" end:"+ts.toString()); } }
测试结果：为什么每次间隔时间是2s，而不是1s.
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