Hi All,

I've been facing a very wierd problem.
I have two classes, A & B under the same package XYZ.

A has a method, a(); and B has a method b(), which calls a().
A is a singleton class.

What's wierd is that for some unknown reason I can't get to the current instance of A, from B's b() and get an Exception which shouldn't even be occuring (since those parts of a() aren't reached during execution)!
And when I can the same bit of code from A's main method, it works!

This is what I mean.. here's how the code looks like:

public class A
{ private static A instance;
  
  //Returns the current instance of this class
    public static A getInstance()
    { if(instance==null)
        instance = new A();  
      return instance;
    }
 
  public void a()
  { System.out.println ("Inside a()");
    //..
    //Some operations..
    //..then..
      if(someVeryRareCondition)
        throw new ExceptionA(reasonOfExceptionString) 
  }//end-of-a()-method
 
  public static void Main(String[] args)
  { A.getInstance().a(); //<--This works, prints the String "Inside a()"
  }
}//end-of-class A
 
public class B
{ public b() 
  { A.getInstance().a(); //<--This does NOT work, get the ExceptionA
  }
}//end-of-classB

Infact, even if b() looked like :

public b() 
  { A objA = A.getInstance(); //--(pt.A)
    objA .a(); //--(pt.B)
  }

Before it reached (pt.A), I'm getting the above mentioned Exception..
There's no other class where such an Exception is ever thrown or caught.
[ExceptionA belongs to the same package XYZ].

Any comments would be greatly appreciated.
Thanks in advance.

Nirmalya

 

 

Are you really sure it's impossible for this exception to occurr?
Cause after all, you are calling method a() from b(), and since you didn't tell what happens inside, it's impossible to judge whether this error is really unreachable.
By the code you gave, I cannot reproduce the error.
(btw This won't compile, but I suppose that's just the example)

 

 

Thanks for the reply..
Here's a brief description of what I'm trying to do:
I am writing a plugin for Eclipse. Class A calls some code in some packages in some external JAR files (no problems faced in using those JAR files).

I stepped thru the debugger. In the code,

public b() 
  { A objA = A.getInstance(); //--(pt.A)
    objA .a(); //--(pt.B)
  }

I wasn't even able to reach A's getInstance() method at pt.A. So its really very wierd for Eclipse to give me that exception when I'm just trying to get A's instance (at pt.A) which does not even call those 3rd party packages. Moreover to ensure that my "someVeryRareCondition" doesn't somehow become true by magic, i inserted a dummy println stmt as soon as the method is entered... currently even this prinltn stmt is not reached!

Any clue? Yes I know its very wierd... we've been trying to figure it out ourselves for almsot day now... Anyways thanks for your time reading thru this.

Regards,
Nirmalya

 

 

It's maybe a silly suggestion, but aren't you by any chance getting the exception from somewhere else (dunno, another thread, in another method that also throws this exception?) Cause I really can't see how you'd get an exception from a()while you're not even entering this method...

 

 

Initially .. we did suspect something similar .. but we later reconfirmed that wasn't the case as its a single-threaded application.

I'll post this question on the eclipse.tools newsgroup and see what they have to say on this. Thanks for taking time to read thru this wierd wierd problem..

Regards,
Nirmalya

 

 

I've just tried this very quickly.

//----File A.java-----
package tmp;

public class A
{
private static A instance;

public static A getInstance()
{
if(instance==null) instance = new A();
return instance;
}

public void a()
{
System.out.println("Inside a");
}

public static void main(String args[])
{
A.getInstance().a();
B objB = new B();
objB.b();
}
}

//----File B.java-----
package tmp;

public class B
{
public void b()
{
System.out.println("Inside b");
A.getInstance().a();
}
}



Worked fine. Without any problems as it should.
I think there is some other condition generating exception and this is not the cause of your exeception.

-Manish.

 

 

And it isn't in the A () constructor?