Understanding Thread.join in Java
Thread.join()
Waits for this thread to die.
Thread.join(long millis)
Waits at most millis milliseconds for this thread to die. A timeout of 0 means to wait forever.
This implementation uses a loop of this.wait calls conditioned on this.isAlive. As a thread terminates the this.notifyAll method is invoked. It is recommended that applications not use wait, notify, or notifyAll on Thread instances.
Thread.join() and Thread.join(long millis) explained with real world example in Image.This implementation uses a loop of this.wait calls conditioned on this.isAlive. As a thread terminates the this.notifyAll method is invoked. It is recommended that applications not use wait, notify, or notifyAll on Thread instances.
Source code (MessageThread.java)
/**
* Thread that prints message in interval of 4 seconds.
*
* @author javaQuery
* @date 29th August, 2016
* @Github: https://github.com/javaquery/Examples
*/
public class MessageThread implements Runnable {
// Display a message, preceded by
// the name of the current thread
static void threadMessage(String message) {
String threadName = Thread.currentThread().getName();
System.out.format("%s: %s%n", threadName, message);
}
@Override
public void run() {
String importantInfo[] = {
"Mares eat oats",
"Does eat oats",
"Little lambs eat ivy",
"A kid will eat ivy too"
};
try {
for (int i = 0; i < importantInfo.length; i++) {
// Pause for 4 seconds
Thread.sleep(4000);
// Print a message
threadMessage(importantInfo[i]);
}
} catch (InterruptedException e) {
threadMessage("I wasn't done!");
}
}
}
Source code (ThreadJoinExample.java)
/**
* Thread join example.
* @author javaQuery
* @date 29th August, 2016
* @Github: https://github.com/javaquery/Examples
*/
public class ThreadJoinExample {
public static void main(String[] args) throws InterruptedException {
Thread t = new Thread(new MessageThread());
// start MessageThread.
t.start();
/**
* Main Thread (ThreadJoinExample) will wait for 't' to finish
* its task in 5 seconds of it will leave.
*/
t.join(5000);
/**
* Main Thread (ThreadJoinExample) will wait until 't' finish its task.
*/
// t.join();
System.out.println("Main Thread left(finish).");
}
}
Output
Thread-0: Mares eat oats Main Thread left(finish). Thread-0: Does eat oats Thread-0: Little lambs eat ivy Thread-0: A kid will eat ivy too
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