并发队列：PriorityBlockingQueue和DelayQueue案例使用

PriorityBlockingQueue使用

import java.util.concurrent.PriorityBlockingQueue;

/**
 * @author ：jiaolian
 * @date ：Created in 2021-02-03 15:44
 * @description：priorityBlockingQueue优先级队列测试
 * @modified By：
 * 公众号:叫练
 */
public class PriorityBlockingQueueTest {

    public static void main(String[] args) {
        m2();
    }

    public static void m2() {
        PriorityBlockingQueue priorityBlockingQueue = new PriorityBlockingQueue<>();
        priorityBlockingQueue.add(new Student("叫练1",22));
        priorityBlockingQueue.add(new Student("叫练2",21));
        priorityBlockingQueue.add(new Student("叫练3",23));
        while (!priorityBlockingQueue.isEmpty()) {
            Student student = null;
            try {
                student = priorityBlockingQueue.take();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println(student);
        }
    }

    private static class Student implements Comparable {
        private String name;
        private int age;

        public Student(String name, int age) {
            this.name = name;
            this.age = age;
        }

        public String getName() {
            return name;
        }

        public int getAge() {
            return age;
        }

        @Override
        public String toString() {
            return "Student{" +
                    "name='" + name + '\'' +
                    ", age=" + age +
                    '}';
        }

        @Override
        public int compareTo(Student o) {
            //从大到小排队
            return this.age - o.getAge();
        }
    }
}

如上代码：PriorityBlockingQueue是优先级队列，PriorityBlockingQueue队列的元素需要实现Comparable接口，完成队列的排序，上述代码中定义了Student类实现Comparable接口，Student的compareTo接口按照age属性从小到大排队，输出结果如下图所示。PriorityBlockingQueue底层是二叉平衡树的数组结构实现出队和入队。

DelayQueue使用

import java.util.concurrent.DelayQueue;
import java.util.concurrent.Delayed;
import java.util.concurrent.TimeUnit;

/**
 * @author ：jiaolian
 * @date ：Created in 2021-02-03 16:28
 * @description：延迟队列测试
 * @modified By：
 * 公众号:叫练
 */
public class DelayQueueTest {

    public static void main(String[] args) throws InterruptedException {
        DelayQueue delayQueue = new DelayQueue();
        delayQueue.add(new Student("叫练1",5));
        delayQueue.add(new Student("叫练2",3));
        delayQueue.add(new Student("叫练3",6));
        while (!delayQueue.isEmpty()) {
            System.out.println(delayQueue.take());
        }
    }


    private static class Student implements Delayed {
        private String name;
        //触发时间/秒
        private long time;

        public String getName() {
            return name;
        }


        public long getTime() {
            return time;
        }

        public Student(String name,  long time) {
            this.name = name;
            this.time = time*1000+System.currentTimeMillis();
        }

        @Override
        public long getDelay(TimeUnit unit) {
            //延迟时间小于0就出队列
            long aa = time - System.currentTimeMillis();
            return aa;
        }

        @Override
        public int compareTo(Delayed o) {
            //时间排序,从小到大排列
            Student student = (Student) o;
            return (int)(this.time - student.getTime());
        }

        @Override
        public String toString() {
            return "Student{" +
                    "name='" + name + '\'' +
                    ", time=" + time +
                    '}';
        }
    }
}

如上代码：DelayQueue是延时队列，只有到指定时间的队列才可以出队列，底层使用优先级队列，上面代码定义Student类需要实现Delayed接口同时需要实现getDelay方法和compareTo方法，getDelay方法用于计算出队列时间，一旦小于0就会出队列；compareTo方法用于按触发时间从小到大排序。执行程序后，学生“叫练2”3秒后出队列；学生“叫练1”5秒后出队列；学生“叫练3”6秒后出队列。执行结果如下图所示。

总结

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