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📜  Java并发-BlockingQueue接口

📅  最后修改于: 2020-11-15 04:00:13             🧑  作者: Mango

java.util.concurrent.BlockingQueue接口是Queue接口的子接口，并且另外支持诸如在获取元素之前等待队列变为非空，以及在存储元素之前等待队列中的空间变为可用等操作。 。

BlockingQueue方法

Sr.No. Method & Description
1

boolean add(E e)

Inserts the specified element into this queue if it is possible to do so immediately without violating capacity restrictions, returning true upon success and throwing an IllegalStateException if no space is currently available.
2

boolean contains(Object o)

Returns true if this queue contains the specified element.
3

int drainTo(Collection c)

Removes all available elements from this queue and adds them to the given collection.
4

int drainTo(Collection c, int maxElements)

Removes at most the given number of available elements from this queue and adds them to the given collection.
5

boolean offer(E e)

Inserts the specified element into this queue if it is possible to do so immediately without violating capacity restrictions, returning true upon success and false if no space is currently available.
6

boolean offer(E e, long timeout, TimeUnit unit)

Inserts the specified element into this queue, waiting up to the specified wait time if necessary for space to become available.

7

E poll(long timeout, TimeUnit unit)

Retrieves and removes the head of this queue, waiting up to the specified wait time if necessary for an element to become available.
8

void put(E e)

Inserts the specified element into this queue, waiting if necessary for space to become available.
9

int remainingCapacity()

Returns the number of additional elements that this queue can ideally (in the absence of memory or resource constraints) accept without blocking, or Integer.MAX_VALUE if there is no intrinsic limit.
10

boolean remove(Object o)

Removes a single instance of the specified element from this queue, if it is present.
11

E take()

Retrieves and removes the head of this queue, waiting if necessary until an element becomes available.

例

以下TestThread程序显示了在基于线程的环境中BlockingQueue接口的用法。

现场演示
import java.util.Random;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.BlockingQueue;

public class TestThread {

   public static void main(final String[] arguments) throws InterruptedException {
      BlockingQueue queue = new ArrayBlockingQueue(10);

      Producer producer = new Producer(queue);
      Consumer consumer = new Consumer(queue);

      new Thread(producer).start();
      new Thread(consumer).start();

      Thread.sleep(4000);
   }  


   static class Producer implements Runnable {
      private BlockingQueue queue;

      public Producer(BlockingQueue queue) {
         this.queue = queue;
      }

      @Override
      public void run() {
         Random random = new Random();

         try {
            int result = random.nextInt(100);
            Thread.sleep(1000);
            queue.put(result);
            System.out.println("Added: " + result);
            
            result = random.nextInt(100);
            Thread.sleep(1000);
            queue.put(result);
            System.out.println("Added: " + result);
            
            result = random.nextInt(100);
            Thread.sleep(1000);
            queue.put(result);
            System.out.println("Added: " + result);
         } catch (InterruptedException e) {
            e.printStackTrace();
         }
      }       
   }

   static class Consumer implements Runnable {
      private BlockingQueue queue;

      public Consumer(BlockingQueue queue) {
         this.queue = queue;
      }
      
      @Override
      public void run() {
         
         try {
            System.out.println("Removed: " + queue.take());
            System.out.println("Removed: " + queue.take());
            System.out.println("Removed: " + queue.take());
         } catch (InterruptedException e) {
            e.printStackTrace();
         }
      }
   }
}

这将产生以下结果。

输出

Added: 52
Removed: 52
Added: 70
Removed: 70
Added: 27
Removed: 27