Understanding the difference between wait() and sleep()

Tell the truth , Except that their execution will make the thread blocked , I don't think they are comparable .

1.wait()、notify() and notifyAll() Methods are Object Methods , Can only be performed in critical areas .

2.wait() The lock identification will be released after execution , The usage scenario is that some threads that do not meet the conditions grab the lock , In order to make it execute after the condition is satisfied , Just call this method . Then wait until the conditions are met , Call again notify() and notifyAll() Let it live, they wake up .

3.wait() After giving up the lock sign , other Runnable The thread in state can execute normally , And be wait The thread of is only notify() and notifyAll() Before they are qualified to enter the lock grabbing army , That is to say, they were Runnable 了 .

4.wait() After entering the blocking state is with sleep() It's different after , be called “ Wait for blocking ”.JVM Will put them in the waiting queue . Of course, this waiting queue is different from that of the lock grabbing army . The lock grabbing army is in a queue full of Runnable Thread in state , Those who continue to sharpen their fists after failing to grab the lock , Their blocking state is called “ Synchronization blocking state ”. That is to say, out of “ Wait for blocking ” The thread of , After being awakened , If you can't grab the lock, it will become Runnable The state of tie Hanhan and others Runnable Tie Hanhan lives together “ Synchronization blocking state ”.

5.sleep() yes Thread Methods , Add time when using , And throw exceptions . It's troublesome , I don't like it a little . When it's called , The lock identification will not be released , Everyone is waiting for it sleep, It's selfish . Of course, threads are not so humanized , it sleep It is to let the thread that communicates priority with it execute first .

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Finally notify() and notifyAll() Words , They are always mentioned above , It's a little unreasonable not to introduce .

 

1.notify() Randomly wake up a person in “ Wait for blocking ” The thread of .

2.notifyAll() As the name suggests, it is to wake up completely in “ Wait for blocking ” The thread of .

We feel , Only one thread can grab the lock , Then let's wake up whether it's just right ？

Remember that , It feels unreliable . Especially in the logic rigorous programming world , Unreliability means risk ！

You wake up one randomly every time , That is to say , There is a chance that a thread will never be awakened ？

therefore ,notifyAll() Would it be more appropriate ？