Java BlockingQueue add()用法及代码示例

BlockingQueue接口的add(E e)方法将在参数中传递的元素插入到Queue的末尾，如果有空间。如果BlockingQueue操作系统的容量受到限制并且没有剩余空间可插入，则它将返回IllegalStateException。

用法:

public void add(E e)

参数：此方法接受强制性参数e，该参数是要插入到BlockingQueue末尾的元素。

返回值：成功插入时此方法返回true。

异常：

• IllegalStateException：如果由于容量限制此时无法添加元素
• NullPointerException ：如果指定的元素为null

注意：BlockingQueue的add()方法已从Java中的Queue类继承。

下面的程序说明BlockingQueue的add()方法：

示例1:

// Java Program Demonstrate add() 
// method of BlockingQueue 
  
import java.util.concurrent.LinkedBlockingDeque; 
import java.util.concurrent.BlockingQueue; 
import java.util.*; 
  
public class GFG { 
    public static void main(String[] args) 
        throws IllegalStateException 
    { 
  
        // create object of BlockingQueue 
        BlockingQueue<Integer> BQ 
            = new LinkedBlockingDeque<Integer>(); 
  
        // Add numbers to the BlockingQueue 
        BQ.add(7855642); 
        BQ.add(35658786); 
        BQ.add(5278367); 
        BQ.add(74381793); 
  
        // before removing print BlockingQueue 
        System.out.println("Blocking Queue: " + BQ); 
    } 
}

Blocking Queue: [7855642, 35658786, 5278367, 74381793]

示例2:

输出：

Exception in thread "main" java.lang.IllegalStateException: Deque full
    at java.util.concurrent.LinkedBlockingDeque.addLast(LinkedBlockingDeque.java:335)
    at java.util.concurrent.LinkedBlockingDeque.add(LinkedBlockingDeque.java:633)
    at GFG.main(GFG.java:23)

示例3:

// Java Program Demonstrate add() 
// method of LinkedBlockingDeque 
// when null is inserted 
  
import java.util.concurrent.LinkedBlockingDeque; 
import java.util.*; 
  
public class GFG { 
    public static void main(String[] args) 
        throws IllegalStateException 
    { 
  
        // create object of LinkedBlockingDeque 
        LinkedBlockingDeque<Integer> BQ 
            = new LinkedBlockingDeque<Integer>(); 
  
        // Add numbers to end of LinkedBlockingDeque 
        BQ.add(7855642); 
        BQ.add(35658786); 
        BQ.add(5278367); 
  
        // NULL 
        BQ.add(null); 
  
        // before removing print Deque 
        System.out.println("Linked Blocking Deque: " + BQ); 
    } 
}

输出：

Exception in thread "main" java.lang.IllegalStateException: Deque full
    at java.util.concurrent.LinkedBlockingDeque.addLast(LinkedBlockingDeque.java:335)
    at java.util.concurrent.LinkedBlockingDeque.add(LinkedBlockingDeque.java:633)
    at GFG.main(GFG.java:25)

参考： https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/BlockingQueue.html#add(E)