The Phaser class is a synchronization aid introduced in Java 7. It allows you to synchronize a group of threads so that they can wait for each other to complete a phase of execution before proceeding to the next one.
A Phaser is similar to a CountDownLatch, but with more advanced features. It allows you to divide your computation into multiple phases, and allows the threads to wait for each other at the end of each phase. A Phaser has a phase number, which starts at zero, and increases each time all the threads arrive at the phaser. The Phaser provides a way for the threads to coordinate and synchronize with each other, allowing them to work on different parts of the computation at the same time.
To use a Phaser in your Java program, you first create a new Phaser object, and then register the threads that will be using it. Once all the threads have been registered, you can start the computation by calling the Phaser’s arriveAndAwaitAdvance() method. This will cause the threads to wait for each other to arrive at the phaser before proceeding to the next phase. You can use the Phaser’s arrive() method to signal that a thread has completed its work for the current phase.