Code Snippets: Thread Interruption

Explain following code snippet:

class ThreadInterrupted extends Thread {
public void run() // called when start method executes.
{
System.out.println("Inside run");
try {
synchronized (this) {
System.out.println("Before calling wait");
wait();
System.out.println("wait is called");
}
} catch (InterruptedException ie) {
System.out.println("value of interrupted():"+interrupted());
System.out.println("Here goes printStackTrace");
ie.printStackTrace();
}
}
public static void main(String[] args) {
ThreadInterrupted threadInterrupted = new ThreadInterrupted();
threadInterrupted.start(); // control goes to run method.
System.out.println ("Before calling interrupt()");
threadInterrupted.interrupt();
}
}

Once you execute this snippet of code the output shown at console looks something like:

Before calling interrupt() Inside run Before calling wait value of interrupted():false Here goes printStackTrace java.lang.InterruptedException at java.lang.Object.wait(Native Method) at java.lang.Object.wait(Unknown Source) at ThreadInterrupted.run (ThreadInterrupted.java:9)

Explaination:
Immediately after start() method is called thread is interrupted.When execution goes inside run() method where a synchornised block of code exists it mean only a single instance of this class can access this piece of code which calls wait() method.The current object of current class invokes interrupt() methos which in turn cause InterruptedException.