The throw question

[Vinoth Kumar Kannan]

package vin_java;

public class ExceptionTest
{
	static public void main(String[] args)
	{
		try
		{
			System.out.println("Inside Try Block Now");
			int i = 5/0;
		}
		catch(Exception ex)
		{
			System.out.println("Inside Catch Block Now");
			
			//Chained Exceptions can be built upto any level
			//use initCause() for those exceptions that dont have the Constructor(String message,Throwable cause)
			NullPointerException nullPointerEx = new NullPointerException("Hello...I'm a new NullPointerException,thrown from the Catch Block ;)");
			nullPointerEx.initCause(new MyException("Vinoth caused this!",new ArithmeticException().initCause(new ClassNotFoundException())));
			
			//finally runs before the below throw actually occurs
			throw nullPointerEx;
			// System.out.println("The line immediately after throw"); //un-reachable code compile error
		}
		finally
		{
			System.out.println("Inside Finally Block Now");
			//this throw will override the throw in the catch block
			throw new MyException(null);
		}
	}
}

class MyException extends Exception
{
	private String message = "No Message Set";
	public MyException(String message)
	{
		if(message != null)
			this.message = message;
	}
	
	public MyException(String message,Throwable cause)
	{
		super(message,cause);
	}
	
	public String toString()
	{
		return "***********************************" + message + "***********************************";
	}
}

When I compile this, i get,

vin_java\ExceptionTest.java:34: unreported exception vin_java.MyException; must be caught or declared to be thrown
                        throw new MyException(null);
                        ^
1 error

Adding 'throws MyException' to main() would solve this, but why am I getting this error in the finally block,while a very similar throw inside catch block works fine.
I just want JVM's default handler to catch the exception I throw from finally. Same with catch is very fine. Default handler gets it.

Is there something i'm doing wrong? Is there any helping explanation?

[David Newton]

"Very similar" does not mean "the same".

An NPE is a RuntimeException. MyException is not. Checked exceptions *must* be either caught, or declared to be thrown. Runtime exceptions require neither.

[Campbell Ritchie]

That looks very similar to what is discussed in this thread.

[Vinoth Kumar Kannan]

Thanks David & Campbell...I completely get that Checked/UnChecked Exceptions
I just have one more question in store, regarding this.
I tried extending 'RuntimeException' class instead of 'Exception' so that my custom exception could be an unchecked one, but i'm getting compile errors like

found   : vin_java.MyException
required: java.lang.Throwable

I just have extended RuntimeException which IS-A Throwable instance,right? though not directly. Can we not make our custom exceptions UnChecked?

[David Newton]

We'd have to see the current code in order to help.

[Vinoth Kumar Kannan]

oops..my mistake,my mistake. works fine when i subclass RuntimeException.
I just used 'RunTimeException' instead of 'RuntimeException'. I got some 7 compile errors..didn just focus on the very first one - cannot find symbol.
really am sorry to bother you people.