package com.pierre;
public class LockGeneration {
public static Object myMonitor = new Object();
public static void main(String[] args) throws InterruptedException {
T1 t1 = new T1();
T2 t2 = new T2();
t1.start();
t2.start();
for (;;) {
Thread.sleep(1000);
}
}
}
class T1 extends Thread {
@Override
public void run() {
System.out.println("T1 started");
super.run();
for (;;) {
try {
synchronized (LockGeneration.myMonitor) {
Thread.sleep(1030);
}
Thread.sleep(10);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
class T2 extends Thread {
@Override
public void run() {
System.out.println("T2 started");
super.run();
for (;;) {
try {
synchronized (LockGeneration.myMonitor) {
Thread.sleep(1050);
}
Thread.sleep(10);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
a thread dump will show for instance:
"Thread-1" prio=6 tid=0x000000001b9be000 nid=0x3c4c waiting for monitor entry [0x000000001c57f000]
java.lang.Thread.State: BLOCKED (on object monitor)
at com.pierre.T2.run(LockGeneration.java:48)
- waiting to lock <0x0000000755ecf6b0> (a java.lang.Object)
Locked ownable synchronizers:
- None
"Thread-0" prio=6 tid=0x000000001b9bd000 nid=0x513c waiting on condition [0x000000001c47f000]
java.lang.Thread.State: TIMED_WAITING (sleeping)
at java.lang.Thread.sleep(Native Method)
at com.pierre.T1.run(LockGeneration.java:27)
- locked <0x0000000755ecf6b0> (a java.lang.Object)
Locked ownable synchronizers:
- None
so the thread (T1 in this case) holding the lock on the object monitor will show
"locked < OBJECT ID > " (the TD shows also the TYPE of the lock, a java.lang.Object)
the thread T1 when sleeping will be in TIMED_WAITING (= wait for on a notification but with a timeout), and waiting on condition
the thread T2 waiting to acquire the lock will be in
BLOCKED (on object monitor) and waiting to lock <0x0000000755ecf6b0> (which is the same OBJECT ID held by T1.
