About Exception and Throwable

[dishlad kumar]

Hi,
I am going to pass my certification in a few days...
I have a confusion over Exception and Throwable with the following code:

Given:

static void test() throws Error {
    if (true) throw new AssertionError();
    System.out.print("test ");
}

public static void main(String[] args) {
    try { test(); }
    catch (Exception ex) { System.out.print("exception "); }
    System.out.print("end ");
}
What is the result?
A.end
B.Compilation fails
C.exception end
D.exception test end
E.A Throwable is thrown by main
F.An Exception is thrown by main

I am hesitating between E and F...Which one is the correct answer?

[Swapnil Sanghai]

You will get the compilation error as you are throwing an error and catching an exception. See the hierarchy structure.

[dishlad kumar]

No compilation error...
I tried to run the code nad the result was:

Exception in thread "main" java.lang.AssertionError
	at Explorer3.test(Explorer3.java:3)
	at Explorer3.main(Explorer3.java:8)

i am a litte bit confused...

[Swapnil Suryakant Prabhavalkar]

Hi,

According to me, following answer is correct:

E.A Throwable is thrown by main

Java compiler only checks whether checked exceptions are caught or not. If method is throwing the checked exception and catch block doesn't specify that exception or superclass of it, then compilation error would occur. Here method is throwing error and compiler would not check if there exist a catch block for error or not. So there would not be any compilation error.

As error is subtype of Throwable , a Throwable is thrown by main.

[Matthew Brown]

Welcome to The Ranch!

One source of the confusion may be that the message displayed by the JVM is a little misleading:

Exception in thread "main" java.lang.AssertionError  

It produces the message "Exception in thread..." when any Throwable is handled by the JVM. Even if it's not actually an Exception object. Errors are in a different branch of the inheritance tree to Exception, but that message still gets shown. Think of it as meaning "exceptional condition" rather than "java.lang.Exception".

And yes, I'd agree: E. If an Exception was thrown it would be caught in the main method, and you'd get some output. But nowhere in the code is catching an Error.

[dishlad kumar]

Thanks guys !!!