public class threaddemo { public static void main(string[] args) throws interruptedexception { object obj1 = new object(); object obj2 = new object(); object obj3 = new object(); thread t1 = new thread(new syncthread(obj1, obj2), "t1"); thread t2 = new thread(new syncthread(obj2, obj3), "t2"); thread t3 = new thread(new syncthread(obj3, obj1), "t3"); t1.start(); thread.sleep(500); t2.start(); thread.sleep(500); t3.start(); } } class syncthread implements runnable{ private object obj1; private object obj2; public syncthread(object o1, object o2){ this.obj1=o1; this.obj2=o2; } @override public void run() { string name = thread.currentthread().getname(); system.out.println(name + " acquiring lock on "+obj1); synchronized (obj1) { system.out.println(name + " acquired lock on "+obj1); work(); system.out.println(name + " acquiring lock on "+obj2); synchronized (obj2) { system.out.println(name + " acquired lock on "+obj2); work(); } system.out.println(name + " released lock on "+obj2); } system.out.println(name + " released lock on "+obj1); system.out.println(name + " finished execution."); } private void work() { try { thread.sleep(30000); } catch (interruptedexception e) { e.printstacktrace(); } } }
you have deadlock problem.
t1 aquires lock obj1. work. in mean time t2 aquires lock obj2 , work. same goes t3 , obj3.
now t1 done first work wants aquire lock of obj2. has wait until t2 finished obj2. t2 waiting t3 finish , release lock obj3. t3 on other hand release lock obj3 if has lock of obj1, blocked t1.
so waiting other 1 finish. definition of deadlock 3 threads.
you can see in output:
t1 acquiring lock on java.lang.object@78f92cc8 t1 acquired lock on java.lang.object@78f92cc8 t2 acquiring lock on java.lang.object@55d2162c t2 acquired lock on java.lang.object@55d2162c t3 acquiring lock on java.lang.object@47122d t3 acquired lock on java.lang.object@47122d t1 acquiring lock on java.lang.object@55d2162c (<-- waiting t2 finish) t2 acquiring lock on java.lang.object@47122d (<--waiting t3 finish) t3 acquiring lock on java.lang.object@78f92cc8 (<-- waiting t1 finish) hope you.
regards, chris
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