java | thread deadlock example

java | thread deadlock example

// An example of deadlock.

// situation comes due to synchronized keyword

class A {

 synchronized void foo(B b) {

String name = Thread.currentThread().getName();   //main thread

System.out.println(name + " entered A.foo");

try {

  Thread.sleep(1000);      //suspended for 1 second

} catch(Exception e) {

  System.out.println("A Interrupted");

}

System.out.println(name + " trying to call B.last()");

b.last();                        //but b is locked by Racing thread

             // solution is use this.last();

 }

 synchronized void last() {

System.out.println("Inside A.last");

 }

}

class B {

 synchronized void bar(A a) {

String name = Thread.currentThread().getName();

System.out.println(name + " entered B.bar");

try {

  Thread.sleep(1000);

} catch(Exception e) {

  System.out.println("B Interrupted");

}

System.out.println(name + " trying to call A.last()");

a.last();          //and here a is locked by main thread and situation comes called            

                                  //Deadlock

 }

 synchronized void last() {

System.out.println("Inside A.last");

 }

}

class Deadlock implements Runnable {

 A a = new A();       // say a address is 1000

 B b = new B();         // say b address is 2000

 Deadlock() {

            //There are two threads

Thread.currentThread().setName("MainThread");  / /first

Thread t = new Thread(this, "Racing Thread");       //second

t.start();//calling of run method for racing thread but after main thread

a.foo(b); // get lock on a by  main thread. and passing b’s reference

System.out.println("Back in main thread");

 }

 public void run()

{

b.bar(a);              // get lock on b in by racing thread.

System.out.println("Back in another thread");

 }

 public static void main(String args[]) {

new Deadlock();

 }

}