BlockingQueue阻塞隊列的使用

1. BlockingQueue是阻塞隊列。它是一個接口，主要的實現類有

2. add方法，隊列添加滿時拋出異常

   public class BlockingQueueTest {
       public static void main(String[] args) {
           test1();
       }
       
       //拋出異常的方法
       public static void test1(){
           BlockingQueue blockingQueue = new ArrayBlockingQueue(3);
           System.out.println(blockingQueue.add(1));
           System.out.println(blockingQueue.add(2));
           System.out.println(blockingQueue.add(3));
   
           System.out.println(blockingQueue.add(4));   //拋出異常
       }
   }
   

   添加第4個時 拋出異常

3. remove方法，隊列為空時，繼續移除元素拋出異常

   public class BlockingQueueTest {
       public static void main(String[] args) {
           test1();
       }
       
       //拋出異常的方法
       public static void test1(){
           BlockingQueue blockingQueue = new ArrayBlockingQueue(3);
           System.out.println(blockingQueue.add(1));
           System.out.println(blockingQueue.add(2));
           System.out.println(blockingQueue.add(3));
   
           System.out.println("=====================================");
   
           System.out.println(blockingQueue.remove());
           System.out.println(blockingQueue.remove());
           System.out.println(blockingQueue.remove());
   
           System.out.println(blockingQueue.remove());    //拋出異常
   
       }
   }
   

   上面只添加了3個元素，下面移除4個元素。當移除第4個元素時，拋出異常

   

4. offer和poll方法，有返回值，不拋出異常

   public class BlockingQueueTest {
       public static void main(String[] args) {
           test2();
       }
       
       //有返回值 不拋出異常
       public static void test2(){
           BlockingQueue blockingQueue = new ArrayBlockingQueue(3);
           System.out.println(blockingQueue.offer(1));
           System.out.println(blockingQueue.offer(2));
           System.out.println(blockingQueue.offer(3));
           System.out.println(blockingQueue.offer(4));         //不拋出異常 返回false
   
           System.out.println("=====================================");
   
           System.out.println(blockingQueue.poll());
           System.out.println(blockingQueue.poll());
           System.out.println(blockingQueue.poll());
   
           System.out.println(blockingQueue.poll());           //不拋出異常   返回null
   
       }
   }
   

   執行結果

   

5. 返回隊首元素

   blockingQueue.element();	//返回隊首元素 如果隊列為null 拋出異常
   blockingQueue.peek()		//返回隊首元素 如果隊列為null 則返回null 不拋出異常
   

6. put方法，隊列滿時阻塞，直到隊列有空位為止

   public class BlockingQueueTest {
       public static void main(String[] args) throws InterruptedException {
           test3();
       }
       public static void test3() throws InterruptedException {
           BlockingQueue blockingQueue = new ArrayBlockingQueue(3);
           blockingQueue.put(1);
           blockingQueue.put(2);
           blockingQueue.put(3);
           blockingQueue.put(4);       //程序在這里阻塞住
       }
   }
   

7. task方法，隊列為空時阻塞，直到隊列有元素為止

   public class BlockingQueueTest {
       public static void main(String[] args) throws InterruptedException {
           test3();
       }
       public static void test3() throws InterruptedException {
           BlockingQueue blockingQueue = new ArrayBlockingQueue(3);
           blockingQueue.put(1);
           blockingQueue.put(2);
           blockingQueue.put(3);
          // blockingQueue.put(4);       //程序在這里阻塞住
   
           System.out.println("======================");
   
           System.out.println(blockingQueue.take());
           System.out.println(blockingQueue.take());
           System.out.println(blockingQueue.take());
           System.out.println(blockingQueue.take());     //程序在這里阻塞住
       }
   }
   

8. 超時等待

   public class BlockingQueueTest {
       public static void main(String[] args) throws InterruptedException {
           test4();
       }
       public static void test4() throws InterruptedException {
           BlockingQueue blockingQueue = new ArrayBlockingQueue(3);
           System.out.println(blockingQueue.offer(1));
           System.out.println(blockingQueue.offer(2));
           System.out.println(blockingQueue.offer(3));
           System.out.println(blockingQueue.offer(4, 2, TimeUnit.SECONDS));   //等待2秒 如果加入成功返回true,否則返回false
   
           System.out.println("======================");
   
           System.out.println(blockingQueue.poll());
           System.out.println(blockingQueue.poll());
           System.out.println(blockingQueue.poll());
           System.out.println(blockingQueue.poll(2,TimeUnit.SECONDS));     //等待2秒 如果有值可以取就返回值，否則返回null
       }
   }
   
   

9. 總結上面4組API

   方法	拋出異常	不拋異常，返回值	阻塞	超時阻塞
   添加	add	offer	put	offer(obj,v,t)
   移除	remove	poll	task	poll(v,t)
   查看隊首	element	peek	—	—