Please help me understand this program's execution and what concepts apply here in the larger sense? An illustration which explains thread(s)/stack(s) creations and destruction would be helpful.
class Joining {
static Thread createThread(final int i, final Thread t1) {
Thread t2 = new Thread() {
public void run() {
System.out.println(i+1);
try {
t1.join();
} catch (InterruptedException ie) {
}
System.out.println(i+2);
}
};
System.out.println(i+3);
t2.start(); //1
System.out.println(i+4);
return t2;
}
public static void main(String[] args) {
createThread(10, createThread(20, Thread.currentThread()));
}
}
Adding some debug-output will probably help you understand the execution:
import static java.lang.Thread.currentThread;
class Joining {
static int count = 0;
static Thread createThread(final int i, final Thread t1) {
System.out.println("Create thread with " + i + " and " + t1.getName());
Thread t2 = new Thread("Thread " + count++) {
public void run() {
System.out.println(currentThread().getName() + ": " + (i+1));
try {
System.out.println(currentThread().getName() + ": join with " + t1.getName());
t1.join();
} catch (InterruptedException ie) {
}
System.out.println(currentThread().getName() + ": " + (i+2));
}
};
System.out.println(currentThread().getName() + ": " + (i+3));
System.out.println(currentThread().getName() + ": starting thread " + t2.getName());
t2.start(); //1
System.out.println(currentThread().getName() + ": " + (i+4));
return t2;
}
public static void main(String[] args) throws InterruptedException {
Thread someThread = createThread(20, currentThread());
System.out.println("After first createThread.");
Thread.sleep(1000);
createThread(10, someThread);
}
}
The output is
Create thread with 20 and main
main: 23
main: starting thread Thread 0
main: 24
After first createThread.
Thread 0: 21
Thread 0: join with main
Create thread with 10 and Thread 0
main: 13
main: starting thread Thread 1
main: 14
Thread 1: 11
Thread 1: join with Thread 0
Thread 0: 22
Thread 1: 12
嗯...对我来说好像t1.join
会永远挂在第一个createThread(20,Thread.currentThread))调用上。
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