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<Student> 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<Student> {        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<Student> delayQueue = new DelayQueue<Student>();        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。