Abstract method

[Shiva Mohan]

http://www.examulator.com
link question

What will happen when you attempt to compile and run the following code?

    
abstract class Hall{
    public abstract void getFireStation();
}
 
public class Haddon extends Hall{
 
    public static void main(String argv[]){
new Haddon().getFireStation();
    }
    public synchronized  void getFireStation(){//abstract class method can be implemented with deiffernt signature
System.out.print("opposite");
    }
}

1) Compile time error, synchronized can only be used in a class that extends Thread
2) Compile time error, malformed method getFireStation in class Hall.
3) Compilation and output of opposite at runtime
4) Compile time error, code within main method is incorrect.

Answer is 3.Abstract method is implemented in subclass with synchronized on it.what is the use of this manner?This is the first time i have got questions in absract method like this? In what other ways of abstract method implemented in subclass in different ways?Please guide me.

[ramya ray]

A non synchronized method can be override to synchronized and vice versa.

[Atul Sawant]

Synochronized modifier is used to make a method accessible to only one thread at a time. This is done by obtaining a lock on a object from which that method was invoked. Any other thread is denied to access that method using SAME object.

You'll learn more about synchronization in THREADS.