Is non-blocking algorithm also apply for insertion and deletion OR only for some condition like no available space/ no elements to consume

Question

Some blogs mentioned that non-blocking algorithm Data Structures will not block calling threads if no space/element to add/consume. They immediately return with Exception or null. But nowhere I have not found How insertion/deletion works in non-blocking algorithms.

Answer 1

It might take different operations when condition is not satisfied. There are four typical forms:

• throw exeption
• return a special value
• block
• time out

For non-blocking implemention, the first two might happen.

Refer the doc of BlockingQueue:

A Queue that additionally supports operations that wait for the queue to become non-empty when retrieving an element, and wait for space to become available in the queue when storing an element.

BlockingQueue methods come in four forms, with different ways of handling operations that cannot be satisfied immediately, but may be satisfied at some point in the future: one throws an exception, the second returns a special value (either null or false, depending on the operation), the third blocks the current thread indefinitely until the operation can succeed, and the fourth blocks for only a given maximum time limit before giving up. These methods are summarized in the following table:

         Throws exception   Special value   Blocks           Times out
Insert   add(e)             offer(e)        put(e)           offer(e, time, unit)
Remove   remove()           poll()          take()           poll(time, unit)
Examine  element()          peek()          not applicable   not applicable