On the role of thread communication, wait and notify

The purpose of thread communication is to enable threads to send signals to each other. In addition, thread communication can also make the thread wait for the signal of other threads. For example, thread B can wait for the signal of thread a, which can be the signal that thread a has processed

Wait() method

-Interrupt the execution of the method, make the thread wait, temporarily give up the use right of the CPU, and allow other threads to use the synchronization method

Notify() method

-Wake up an end wait of a waiting thread due to the use of this synchronizer

Notifyall() method

Wake up all threads that are waiting due to the use of this synchronization method and end the wait

When to use the wait method

When a variable is used in the synchronization method used by a thread, and this variable needs to be modified by other threads to meet the needs of this thread, you can use the wait () method in the synchronization method

Here, I take an example in class to briefly describe the functions of wait and notify

We already know that when a multi thread is enabled, such as ticket sales, the order of tickets sold in each window is random. If we have two ticket sales windows, it is stipulated that 100 tickets must be sold in turn. After window a sells one ticket, the next ticket must be sold by window B. how can we realize this function?

First of all, I think an IF statement can be set. If (I% 2 = = 0) then thread 1 will run, otherwise thread 2 will run. However, the operation of thread 1 and thread 2 is random, and the size of I cannot be used to determine who runs

Then we can use wait () and notify () in the thread

After thread 1 runs, wait, and then thread 2 runs. After thread 2 runs, wake up thread 1, and then run again

After thread 1 runs, wait, then thread 2 runs, and then wake up thread 1 after thread 2 runs

In this way, thread 1 and thread 2 can be run in turn

We have printed 10 numbers as examples to write programs. A total of 2 classes myprint and myprinttest are built

Myprint. java

The results are shown in the figure

You can see that thread 1 and thread 2 have been printed alternately

Just understand the operation process

When I < 10, print thread 1 and then execute wake-up. Since there is no previous thread, this step will not be executed. Then thread 1 waits. After executing thread 2, wake up the previous thread, that is, thread 1, and then print thread 1,

This process continues until it jumps out of the loop, so we can take turns

summary

The above is all about the role of thread communication wait and notify in this paper. I hope it will be helpful to you. Interested friends can continue to refer to other related topics on this site. If there are deficiencies, please leave a message to point out. Thank you for your support!