实现PriorityBlockingQueue API的Java程序

PriorityBlockingQueue 是一个无界阻塞队列，它使用与 PriorityQueue 类相同的排序规则并提供阻塞检索操作。添加名称的“阻塞”部分以暗示线程将阻塞等待，直到队列中有可用的项目。此类不允许空元素。依赖于自然排序的优先级队列也不允许插入不可比较的对象（这样做会导致 ClassCastException）。

它实现了 Serializable、Iterable、Collection、BlockingQueue、Queue 接口并扩展了 AbstractQueue 类。

宣言：

public class PriorityBlockingQueue extends AbstractQueue implements BlockingQueue, Serializable
// Here, E is the type of elements held in this collection

java.lang.Object
   java.util.AbstractCollection
       java.util.AbstractQueue
          java.util.concurrent.PriorityBlockingQueue

执行：

例子

Java

// Java Program to Implement PriorityBlockingQueue API
 
// Importing concurrent classes from
// java.util package
import java.util.concurrent.PriorityBlockingQueue;
import java.util.concurrent.TimeUnit;
 
// Class for PriorityQueue
public class GFG {
    // Main driver method
    public static void main(String[] args)
        throws InterruptedException
    {
        // Creating a new object of PriorityBlockingQueue
        // Declaring Integer type object
        PriorityBlockingQueue priorityBlockingQueue
            = new PriorityBlockingQueue<>();
 
        // Creation of a thread
        new Thread(() -> {
            // Display message
            System.out.println("Waiting to poll ...");
 
            // Try block to check for exceptions
            try {
 
                // Condition check
                while (true) {
 
                    // Return (integer) value at head of
                    // queue of PriorityBlockingQueue
                    Integer poll
                        = priorityBlockingQueue.take();
 
                    // Display and print element returned in
                    // PriorityBlockingQueue
                    System.out.println("Polled : " + poll);
 
                    // Pause the execution of current thread
                    // for certain amount of time using
                    // toMills() method() to showcase
                    // working of PriorityBlockingQueue
                    Thread.sleep(
                        TimeUnit.SECONDS.toMillis(1));
                }
            }
 
            // Catch block to handle exceptions if any
            catch (InterruptedException e) {
 
                // Print and display the line number
                // where exception/s occured
                e.printStackTrace();
            }
 
            // Execution of thread begins with
            // use of start() method
        }).start();
 
        // Custom elememts inputs
        // 1, 2, 3 to priorityBlockingQueue
 
        // Pausing execution of first thread
        Thread.sleep(TimeUnit.SECONDS.toMillis(2));
 
        // Insert parameter element-> 1 to method
        // at the tail of priority queue
        priorityBlockingQueue.add(1);
 
        // Pausing execution of second thread
        Thread.sleep(TimeUnit.SECONDS.toMillis(2));
 
        // Insert parameter element-> 2 to method
        // at the tail of priority queue
        priorityBlockingQueue.add(2);
 
        // pausing execution of third thread
        Thread.sleep(TimeUnit.SECONDS.toMillis(2));
 
        // Insert parameter element-> 3 to method
        // at the tail of priority queue
        priorityBlockingQueue.add(3);
    }
}

输出：