DelayQueue的使用

DelayQueue的应用

转：http://ideasforjava.iteye.com/blog/657384

DelayQueue

是一个无界的BlockingQueue，用于放置实现了Delayed接口的对象，其中的对象只能在其到期时才能从队列中取走。这种队列是有序的，即队头对象的延迟到期时间最长。注意：不能将null元素放置到这种队列中。

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Delayed

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一种混合风格的接口，用来标记那些应该在给定延迟时间之后执行的对象。

此接口的实现必须定义一个 compareTo 方法，该方法提供与此接口的 getDelay 方法一致的排序。

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下面的代码模拟一个考试的日子，考试时间为120分钟，30分钟后才可交卷，当时间到了，或学生都交完卷了者考试结束。线程的关闭参考Java编程思想中例子，将exec传给Student的一个内部类，通过他来关闭。

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package?com.woxiaoe.study.thread; ????import?java.util.Random; ?? import?java.util.concurrent.DelayQueue; ?? import?java.util.concurrent.Delayed; ?? import?java.util.concurrent.ExecutorService; ?? import?java.util.concurrent.Executors; ?? import?java.util.concurrent.TimeUnit; ?? ??/** ??*?模拟考试，时间为120分钟，学生可以再30分钟后交卷， ??*?当学生都交完了?或?时间到者考试结束 ??*?@author?小e ??* ??*?2010-4-30?下午11:14:25 ??*/??class?Student?implements?Runnable,Delayed{ ?? ????private?String?name; ?? ????private?long?submitTime;//交卷时间 ?? ????private?long?workTime;//考试时间 ?? ????public?Student()?{ ?? ????????//?TODO?Auto-generated?constructor?stub ?? ????} ??????public?Student(String?name,?long?submitTime)?{ ?? ????????super(); ?? ????????this.name?=?name; ?? ????????workTime?=?submitTime; ??????????//都转为转为ns ?? ????????this.submitTime?=?TimeUnit.NANOSECONDS.convert(submitTime,?TimeUnit.MILLISECONDS)?+?System.nanoTime(); ?? ????} ????????@Override?? ????public?void?run()?{ ?? ????????System.out.println(name?+?"?交卷,用时"?+?workTime/100?+?"分钟"); ?? ????} ????????@Override?? ????public?long?getDelay(TimeUnit?unit)?{ ?? ????????return?unit.convert(submitTime?-?System.nanoTime(),?unit.NANOSECONDS); ?? ????} ????????@Override?? ????public?int?compareTo(Delayed?o)?{ ?? ????????Student?that?=?(Student)?o; ??????????return?submitTime?>?that.submitTime?1:(submitTime?<?that.submitTime???-1?:?0); ?? ????} ??????public?static?class?EndExam?extends?Student{ ?? ????????private?ExecutorService?exec; ?? ????????public?EndExam(int?submitTime,ExecutorService?exec)?{ ?? ????????????super(null,submitTime); ?? ????????????this.exec?=?exec; ?? ????????} ??????????@Override?? ????????public?void?run()?{ ?? ????????????exec.shutdownNow(); ??????????} ??????} ?????? ??} ??class?Teacher?implements?Runnable{ ?? ????private?DelayQueue<Student>?students; ?? ????private?ExecutorService?exec; ?? ???? ??????public?Teacher(DelayQueue<Student>?students,ExecutorService?exec)?{ ?? ????????super(); ?? ????????this.students?=?students; ?? ????????this.exec?=?exec; ?? ????} ??????????@Override?? ????public?void?run()?{ ?? ????????try?{ ?? ????????????System.out.println("考试开始……"); ?? ????????????while?(!Thread.interrupted())?{ ?? ????????????????students.take().run(); ??????????????} ??????????????System.out.println("考试结束……"); ?? ????????}?catch?(InterruptedException?e)?{ ?? ????????????e.printStackTrace(); ??????????} ????????} ?????? ??} ??public?class?Exam?{ ?? ????static?final?int?STUDENT_SIZE?=?45; ?? ????public?static?void?main(String[]?args)?{ ?? ????????Random?r?=?new?Random(); ?? ????????DelayQueue<Student>?students?=?new?DelayQueue<Student>(); ?? ????????ExecutorService?exec?=?Executors.newCachedThreadPool(); ??????????for(int?i?=?0;?i?<?STUDENT_SIZE;?i++){ ?? ????????????students.put(new?Student("学生"?+?(?i?+?1),?3000?+?r.nextInt(9000))); ?? ????????} ??????????students.put(new?Student.EndExam(12000,exec));//1200为考试结束时间 ?? ????????exec.execute(new?Teacher(students,?exec)); ?? ???????? ??????} ????}??

?Output:

考试开始…… 学生19 交卷,用时35分钟学生16 交卷,用时40分钟学生7 交卷,用时42分钟学生14 交卷,用时52分钟学生15 交卷,用时54分钟学生1 交卷,用时57分钟学生11 交卷,用时62分钟学生2 交卷,用时71分钟学生13 交卷,用时73分钟学生3 交卷,用时78分钟学生20 交卷,用时85分钟学生17 交卷,用时85分钟学生18 交卷,用时90分钟学生6 交卷,用时94分钟学生9 交卷,用时97分钟学生8 交卷,用时102分钟学生12 交卷,用时103分钟学生5 交卷,用时104分钟学生10 交卷,用时108分钟学生4 交卷,用时112分钟考试结束……