Sychronizers

Question 1

High-level abstractions for synchronizing activities of two or more threads are known is?

Answer 1

Synchronizers

Question 2

List the sychronizers provided in the java.util.concurrent library?

Answer 2

Semaphore, Phaser, CountDownLatch, and Exchanger, CyclicBarrier

Question 3

Explain Semaphore?

Answer 3

A semaphore controls access to shared resources. A semaphore maintains a counter to specify the number of resources that the semaphore controls.
Example: ATM

Question 4

A synchronizer that controls access to a fixed number of shared resources is?
Example controlling access to two ATM machines.

Answer 4

Semaphrore.

Question 5

Explain CountDownLatch

Answer 5

This synchronizer allows one or more threads to wait for a countdown to complete.
Example: On your mark, get set, go!

Question 6

What synchronizer allows one or more threads to wait for a countdown to complete.
5,4,3,2,1 go!

Answer 6

CountDownLatch

Question 7

Explain Exchanger

Answer 7

The Exchanger class is meant for exchanging data between two threads. What Exchanger does is something very simple: it waits until both the threads have called the exchange() method.

Question 8

What synchronizer is meant for exchanging data between two threads.

Answer 8

Exchanger

Question 9

Explain CyclicBarrier

Answer 9

The CyclicBarrier is used to suspend treads until a predefined execution point is reached.
Wait for four players to arrive.

Question 10

What synchronizer waits for a fixed number of threads to be waiting before starting execution.

Answer 10

CyclicBarrier

Question 11

Explain Phaser

Answer 11

Phaser is a useful feature when few independent threads have to work in phases to complete a task.