阻塞队列(BlockingQueue)

阅读目录

• 阻塞队列：
  •  一、ArrayBlockingQueue
  • 二、SynchronizeousQueue：生产一个消费一个
  • 三、PriorityBlockingQueue：阻塞优先队列

 

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阻塞队列：

Queue接口与List、Set同一级别，都是继承了Collection接口。LinkedList实现了Queue接口。

BlockingQueue接口的实现类

 BlockingQUeue的核心方法

 一、ArrayBlockingQueue

1、抛出异常：

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BlockingQueue<String> queue = new ArrayBlockingQueue<>(3); // 1、抛出异常：add/remove System.out.println(queue.add("a")); System.out.println(queue.add("b")); System.out.println(queue.add("c")); // 超出队列长度报错：Queue full // System.out.println(queue.add("x")); queue.remove(); queue.remove(); queue.remove(); // 队列中没有元素报错：NoSuchElementException //queue.remove();

2、特殊值

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BlockingQueue<String> queue = new ArrayBlockingQueue<>(3); // 2、特殊值：offer/poll System.out.println(queue.offer("a")); System.out.println(queue.offer("b")); System.out.println(queue.offer("c")); // 插入不进去元素会返回false System.out.println(queue.offer("x")); System.out.println(queue.poll()); System.out.println(queue.poll()); System.out.println(queue.poll()); // 取不到数据会返回null System.out.println(queue.poll());

3、阻塞

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BlockingQueue<String> queue = new ArrayBlockingQueue<>(3); // 3、阻塞 queue.put("a"); queue.put("b"); queue.put("c"); // 队列插入不了数据，会一直卡住 // queue.put("x"); System.out.println(queue.take()); System.out.println(queue.take()); System.out.println(queue.take()); // 检索并删除此队列的头，如有必要，请等待直到元素可用 System.out.println(queue.take());

4、超时

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BlockingQueue<String> queue = new ArrayBlockingQueue<>(3); // 3、超时 System.out.println(queue.offer("a", 2L, TimeUnit.SECONDS)); System.out.println(queue.offer("b", 2L, TimeUnit.SECONDS)); System.out.println(queue.offer("c", 2L, TimeUnit.SECONDS)); // 队列已满会等待指定的时间，返回false System.out.println(queue.offer("x", 2L, TimeUnit.SECONDS)); System.out.println(queue.poll(2L, TimeUnit.SECONDS)); System.out.println(queue.poll(2L, TimeUnit.SECONDS)); System.out.println(queue.poll(2L, TimeUnit.SECONDS)); // 队列已满会等待指定的时间，返回null System.out.println(queue.poll(2L, TimeUnit.SECONDS));

二、SynchronizeousQueue：生产一个消费一个

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import java.util.concurrent.ArrayBlockingQueue; import java.util.concurrent.BlockingQueue; import java.util.concurrent.SynchronousQueue; import java.util.concurrent.TimeUnit; import java.util.concurrent.locks.Lock; import java.util.concurrent.locks.ReentrantLock;   /**  * @author zhangzhixi  * @date 2021-4-20 22:08  */ public class Demo_05_阻塞队列 {     public static void main(String[] args) throws InterruptedException {         SynchronousQueue<String> queue = new SynchronousQueue<>();         // 一个线程用来生产         new Thread(() -> {             try {                 System.out.println(Thread.currentThread().getName() + "\t put:" + "a");                 queue.put("a");                 System.out.println(Thread.currentThread().getName() + "\t put:" + "b");                 queue.put("b");                 System.out.println(Thread.currentThread().getName() + "\t put:" + "c");                 queue.put("c");             } catch (InterruptedException e) {                 e.printStackTrace();             }         }, "AAA").start();         // 一个线程用来消费         new Thread(() -> {             try {                 TimeUnit.SECONDS.sleep(3);                 System.out.println(Thread.currentThread().getName() +"\t释放 " +queue.take());                 TimeUnit.SECONDS.sleep(3);                 System.out.println(Thread.currentThread().getName() +"\t释放 " +queue.take());                 TimeUnit.SECONDS.sleep(3);                 System.out.println(Thread.currentThread().getName() +"\t释放 " +queue.take());             } catch (InterruptedException e) {                 e.printStackTrace();             }         }, "BBB").start();       } }

三、PriorityBlockingQueue：阻塞优先队列

PriorityBlockingQueue是一个无界队列，它没有限制，在内存允许的情况下可以无限添加元素；它又是具有优先级的队列，是通过构造函数传入的对象来判断，传入的对象必须实现comparable接口。

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public static void main(String[] args) {         // 1、新建一个优先阻塞队列         BlockingQueue<Person> blockingQueue = new PriorityBlockingQueue<>();         Person per = null;         // 2、添加数据         blockingQueue.add(new Person(6, "张三", 20));         blockingQueue.add(new Person(5, "李四", 20));         blockingQueue.add(new Person(1, "王五", 28));         // 3、取出数据         blockingQueue.forEach(System.out::println); }   class Person implements Comparable<Person> {     private Integer id;     private String name;     private Integer age;       public Person() {     }       public Person(Integer id, String name, Integer age) {         this.id = id;         this.name = name;         this.age = age;     }         @Override     public int compareTo(Person o) {         // 比较规则，先按照age进行从小到大排序，如果年龄一样再按照id进行从小到大排序         if (this.age.compareTo(o.age) == 0) {             return this.id.compareTo(o.id);         }         return this.age.compareTo(o.age);     }       @Override     public String toString() {         return "Person{" +                 "id=" + id +                 ", name='" + name + '\'' +                 ", age=" + age +                 '}';     } }

结果：

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Person{id=5, name='李四', age=20} Person{id=6, name='张三', age=20} Person{id=1, name='王五', age=28}