Sample to show deadlocks in a Java Application

This sample application shows an example of a deadlock. Following is the definition of "deadlock" according to Java Tutorial

Deadlock describes a situation where two or more threads are blocked forever, waiting for each other.

In this application, there are two threads trying to acquire two locks.

How to run

The application will throw Out of Memory error after some time when you run the application with default parameters.

java -Xms1g -Xmx1g -jar target/deadlock.jar

How to detect a deadlock

Take a thread dump (using jstack <pid> command or jcmd <pid> Thread.print).

The thread dump should show the Java level deadlock details as follows.

Found one Java-level deadlock:
=============================
"Thread Group  1-2":
  waiting to lock monitor 0x00007f8ab4003a78 (object 0x00000000eaca1488, a java.lang.Object),
  which is held by "Thread Group  1-1"
"Thread Group  1-1":
  waiting to lock monitor 0x00007f8ab4006518 (object 0x00000000eaca1498, a java.lang.Object),
  which is held by "Thread Group  1-2"

Java stack information for the threads listed above:
===================================================
"Thread Group  1-2":
        at com.github.chrishantha.sample.deadlock.DeadlockApplication$SampleLockThread.run(DeadlockApplication.java:54)
        - waiting to lock <0x00000000eaca1488> (a java.lang.Object)
        - locked <0x00000000eaca1498> (a java.lang.Object)
"Thread Group  1-1":
        at com.github.chrishantha.sample.deadlock.DeadlockApplication$SampleLockThread.run(DeadlockApplication.java:54)
        - waiting to lock <0x00000000eaca1498> (a java.lang.Object)
        - locked <0x00000000eaca1488> (a java.lang.Object)

Found 1 deadlock.