Java LinkedTransferQueue getWaitingConsumerCount()用法及代碼示例

java.util.concurrent.LinkedTransferQueue.getWaitingConsumerCount()方法從LinkedTransferQueue(LTQ)返回等待通過take()或定時輪詢接收元素的使用者數量。此處的消費者將閱讀LTQ中的元素。生產者將向LTQ添加元素。僅當多個線程正在運行時，即生產者正在傳輸消息而消費者正在同時接收它們時，此方法才有用。消費者將嘗試閱讀LTQ的標題。如果它們不能(空LTQ或頭部已被拿走)，則稱它們正在等待。消費者將等到他們讀懂頭部或經過一定的時限為止。當生產者通過transfer()添加到LTQ時，據說它被阻止了。這意味著生產者必須等到消費者讀取該元素以向LTQ添加另一個元素。

用法:

public int getWaitingConsumerCount()

參數：此方法不接受任何參數。

返回值：此方法返回一個整數值，該整數值是通過take()獲得的等待LTQ頭部的使用者數量。

例：下麵的程序使用一個生產者和3個消費者。生產者發送3條消息。首先調用take()的使用者將收到最新消息。因此，該程序的不同執行可能導致不同的使用者獲得不同的消息。

// Java program to show LinkedTransferQueue 
// getWaitingConsumerCount() method 
  
import java.util.concurrent.*; 
  
public class GFG { 
  
    // create object of LinkedTransferQueue 
    LinkedTransferQueue<Integer> LTQ 
        = new LinkedTransferQueue<>(); 
  
    class Producer implements Runnable { 
  
        @Override
        public void run() 
        { 
            for (int i = 0; i < 3; i++) { 
                try { 
                    System.out.println("Producer is"
                                       + " waiting to transfer..."); 
  
                    // add 0, 1, 2 to LTQ 
                    LTQ.transfer(i); 
                    System.out.println("Producer "
                                       + "transferred element: " + i); 
  
                    // display how many consumers are waiting 
                    // after producer has transferred element 
                    System.out.println("Waiting consumer "
                                       + "count after transfer: "
                                       + LTQ 
                                             .getWaitingConsumerCount()); 
                } 
                catch (InterruptedException e) { 
                    e.printStackTrace(); 
                } 
            } 
        } 
    } 
  
    class Consumer implements Runnable { 
        int id; 
        Consumer(int id) 
        { 
            this.id = id; 
        } 
  
        @Override
        public void run() 
        { 
            try { 
                System.out.println("Consumer "
                                   + id 
                                   + " is waiting to "
                                   + "take element..."); 
  
                // display how many consumers are waiting 
                // before a consumer has taken element from LTQ 
                System.out.println("Waiting consumer"
                                   + " count before take: "
                                   + LTQ 
                                         .getWaitingConsumerCount()); 
  
                Integer s = LTQ.take(); 
                System.out.println("Consumer "
                                   + id 
                                   + " received Element: "
                                   + s); 
            } 
            catch (InterruptedException e) { 
                e.printStackTrace(); 
            } 
        } 
    } 
  
    public static void main(String[] args) throws InterruptedException 
    { 
        // class object to keep common LTQ for all consumers 
        //(alternative: LTQ can be declared static) 
        GFG obj = new GFG(); 
  
        // enabling multiple threads 
        ExecutorService exService 
            = Executors.newFixedThreadPool(3); 
  
        // declare one producer and 3 consumers 
        Producer producer = obj.new Producer(); 
        Consumer consumer0 = obj.new Consumer(0); 
        Consumer consumer1 = obj.new Consumer(1); 
        Consumer consumer2 = obj.new Consumer(2); 
  
        // start producer and consumers 
        exService.execute(producer); 
        exService.execute(consumer0); 
        exService.execute(consumer1); 
        exService.execute(consumer2); 
  
        // stop 
        exService.shutdown(); 
    } 
}

輸出：
Output in NetBeans 8.2

注意：顯示了NetBeans 8.2中的輸出。建議在本地嘗試此示例，因為它使用multi-threading。聯機IDE服務器可能不支持此函數，或者讓您添加此類負載，從而導致超出時間限製錯誤。

參考： https://docs.oracle.com/javase/9/docs/api/java/util/concurrent/LinkedTransferQueue.html#getWaitingConsumerCount–

相關用法

注：本文由純淨天空篩選整理自sreeragiyer大神的英文原創作品 LinkedTransferQueue getWaitingConsumerCount() method in Java with Examples。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。