【Java】并发队列：PriorityBlockingQueue和DelayQueue案例使用

• Z时代
• 2024-01-10
• 分类：技术分享

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();
}
}
}

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 +
'}';
}
}
}

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。

总结

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