Common methods of threads

join()

public final synchronized void join(long millis) throws InterruptedException {
 long base = System.currentTimeMillis();
 long now = 0;
 if (millis < 0) {
 throw new IllegalArgumentException(&quot;timeout value is negative&quot;);
 }
 if (millis == 0) {
 while (isAlive()) {
 wait(0);
 }
 } else {
 while (isAlive()) {
 long delay = millis - now;
 if (delay <= 0) {
 break;
 }
 wait(delay);
 now = System.currentTimeMillis() - base;
 }
 }
}


if (millis < 0) { throw new IllegalArgumentException(&quot;timeout value is negative&quot;);}

Determine whether the timeout is less than  0, If it is less than 0, It will be thrown out. IllegalArgumentException abnormal

if (millis == 0) { while (isAlive()) { wait(0); } }

millis  be equal to  0  It means infinite waiting , Until the thread finishes executing isAlive Determine whether the child thread is an active thread , Yes, I have been waiting

wait(delay);

It can be seen that ,join() The bottom layer of the method is still through wait() Realized .

In actual use , If in main Method enables a new thread , And it was called in the main thread. join() Method , Then the actual effect will be shown as ： The main thread will wait for the sub thread to finish executing before continuing .

yield()

public static native void yield();


yield() Method is called java Local method , The bottom is made up of C perhaps C++ Realized .

yield() The meaning of the method is ： Give the thread scheduler a current thread willing to sell  CPU  Information about the right to use . But the thread scheduler does not necessarily respond to this request immediately , Will not even respond .

sleep()

public static native void sleep(long millis) throws InterruptedException;


sleep Make the current thread （ That is to call sleep Method is suspended for a period of time ）, Give other threads a chance to run , And it doesn't consider the priority of other threads , And don't release the resource lock , That is to say, if there is synchronized Synchronized block , Other threads still cannot access the shared data

When the thread executes sleep After method , The thread will go to sleep , Until the end of time

sleep Methods need to throw or catch exceptions , Because threads may be interrupted during sleep ,

wait() and wait(time)

wait() Its function is to let the current thread enter the waiting state ,wait() It also causes the current thread to release the lock it holds . Until another thread calls the  notify()  Method or  notifyAll()  Method , The current thread will be awakened to enter the ready state


public final void wait() throws InterruptedException {
 wait(0);
}
 
public final native void wait(long timeout) throws InterruptedException;


wait()  Implementation is also called wait(long timeout) Method , What time brings in is 0

wait(long timeout) Method is called at the bottom java Local method , from C perhaps C++ Realization .