阻塞队列添加元素的几个方法及区别 

boolean add(E e);
boolean offer(E e);
boolean offer(E e, long timeout, TimeUnit unit) throws InterruptedException;
void put(E e) throws InterruptedException;
 
public boolean add(E e) {
    if (offer(e))
        return true;
    else
        throw new IllegalStateException("Queue full");
}

add 
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.
When using a capacity-restricted queue, it is generally preferable to use  offer.
 
当使用容量受限的队列时，通常最好使用offer

  
offer   
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.  
When using a capacity-restricted queue, this method is generally preferable to add, 
which can fail to insert an element only by throwing an exception.
  
  
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.
        
   
put
Inserts the specified element into this queue, waiting if necessary for space to become available.
    


例子

		
BlockingQueue q = new ArrayBlockingQueue<>(3);
q.add("a");
q.add("b");
q.add("c");
		
// 队列满了
// 立即 返回 false
boolean result = q.offer("d");
System.out.println("offer result "+result);
		
// 等待 1秒后 返回 false
result = q.offer("d",1,TimeUnit.SECONDS);
System.out.println("offer with timeout result "+result);

try {
		    q.add("d");
}catch(Throwable e) {
    // java.lang.IllegalStateException: Queue full
    System.out.println("add error,"+e);
}

// put 方法会一直阻塞
q.put("d");


 java中的队列介绍