// These are the two resource objects we'll try to get locks for
final Object resource1 = "resource1";
final Object resource2 = "resource2";
// Here's the first thread. It tries to lock resource1 then resource2
Thread t1 = new Thread() {
public void run() {
// Lock resource 1
synchronized(resource1) {
System.out.println("Thread 1: locked resource 1");
// Pause for a bit, simulating some file I/O or something.
// Basically, we just want to give the other thread a chance to
// run. Threads and deadlock are asynchronous things, but we're
// trying to force deadlock to happen here...
try { Thread.sleep(50); } catch (InterruptedException e) {}
// Now wait 'till we can get a lock on resource 2
synchronized(resource2) {
System.out.println("Thread 1: locked resource 2");
}
}
}
};
// Here's the second thread. It tries to lock resource2 then resource1
Thread t2 = new Thread() {
public void run() {
// This thread locks resource 2 right away
synchronized(resource2) {
System.out.println("Thread 2: locked resource 2");
// Then it pauses, for the same reason as the first thread does
try { Thread.sleep(50); } catch (InterruptedException e) {}
// Then it tries to lock resource1. But wait! Thread 1 locked
// resource1, and won't release it 'till it gets a lock on
// resource2. This thread holds the lock on resource2, and won't
// release it 'till it gets resource1. We're at an impasse. Neither
// thread can run, and the program freezes up.
synchronized(resource1) {
System.out.println("Thread 2: locked resource 1");
}
}
}
};
// Start the two threads. If all goes as planned, deadlock will occur,
// and the program will never exit.
t1.start();
t2.start();
