What are the usage of Blocking queues ?

BlockingQueue

• provides blocking put and take methods.
• If the queue is full, put blocks until space becomes available.
• If queue is empty, take blocks until an element is available.

Producer-Consumer design using BlockingQueue

• Producers place data onto the queue as it becomes available
• Consumer retrieves data from the queue when they are ready to take 
• Example 
• One person washes the dishes and place them in a rack - Producer
• Other person take the dishes from the rack and dries them - Consumer
       ---- "consumes" wet dishes -> "produces" dry dishes
   
• Here, dish rack acts as a BlockingQueue
  If there is no dish in the rack, consumer waits until dishes are available in rack
  If rack fills up, producer stops washing until there is more space.