Mock exam question

[santhoshkumar samala]

 
 
public class BriarMill extends Thread{
    public static void main(String argv[]){
BriarMill bm = new BriarMill();
bm.go();
    }
    public void go(){
start();
    }
    public  void payBill(){
try{
    wait();
}catch(InterruptedException ie){}
System.out.println("done");
 
    }
    public void run(){
payBill();
notifyAll();
    }
 
}
 
 
 1)Compilation but runtime error. 
 2) Compilation and output of done at runtime 
 3) Compilation but no output at runtime, the program will run and wait  with no output. 
 4) Compile time error 
 
  

Answer given is 1, when I compile and run Iam getting runtime exception.. but I have two queries about this question

1)In k&b book it is mentioned that wait,notify and notify all must be called from synchronized block, so why I am not getting compile error here?

2)can we call start() method like above?
[ December 19, 2005: Message edited by: santoshkumar samala ]

[Leonardo Rafaeli]

runtime exception because the wait() is not on a synchronized block

[Naresh Gunda]

In k&b book it is mentioned that wait,notify and notify all must be called from synchronized block,

Yes. Otherwise Runtime Exception. No compilation error.

java.lang.IllegalMonitorStateException: current thread not owner

[Marcus Green]

This question (originally) comes from one of my mock exams, and it includes the following explanation with the answer.

Compilation but runtime error.

At runtime an error indicating java.lang.IllegalMonitorStateException because the wait call is not within synchronized code. Changing the signature of payBill to public synchronized void payBilll would remove the runtime error, causing the program to run and then pause with no output.

Does the explanation look correct, and if so is there something I can do to change the answer to make the explanation more clear?
[ December 19, 2005: Message edited by: Marcus Green ]

[santhoshkumar samala]

Thanks Marcus,

I have not seen any explanation there, may be because I am accessing as guest