Constructor

[Thiru Thangavelu]

There is no exception thrown in class A. How is it possible to instantiate the class A inside the try.. catch. I expected a error, "there is no exception thrown in class A". Can anyone clarify this?

import java.io.*;
class A {
         A() { // throws IOException {
                System.out.println ("Executing class A constructor");
                //throw new IOException();
          }
}
public class B extends A {
          B() {
                System.out.println ("Executing class B constructor");
           }
           public static void main ( String args[] ) {
                   try {
                   A a = new A();
                   } catch ( Exception e) {
                               System.out.println( e.getMessage() );
                   }
                   //A a = new A();
           }
}

[ June 19, 2002: Message edited by: Thiru Thangavelu ]

[Corey McGlone]

Notice that your catch block catches "Exceptions". It doesn't catch IOException. One of the descendents of Exception is RuntimeException. As RuntimeExceptions need not be declared, you are free to try to catch them at any time. If you change that catch block to catch an IOException, I'll bet you'll get the compiler error you expected.
Corey
[ June 19, 2002: Message edited by: Corey McGlone ]

[Thiru Thangavelu]

Even this compiles fine how?

import java.io.*;
class A {
}
public class B extends A {
           public static void main ( String args[] ) {
                   try {
                   A a = new B();
                   } catch ( Exception e) {
                               System.out.println( e.getMessage() );
                   }
                   A a1 = new B();
           }
}

[Thiru Thangavelu]

Thanks as always Corey,
that cleared my doubt.

[Jose Botella]

Exception is the only checked exception that can be declared within a catch clause without being thrown.

[Thiru Thangavelu]

how about Throwable?

[Corey McGlone]

Originally posted by Thiru Thangavelu:
how about Throwable?

Only descendents of Exception (with the exclusion of RuntimeException) are considered checked exceptions. Anything else (RuntimeException and anything higher on the inheritance hierarchy) is not checked.
Corey

[Paul Villangca]

Besides, Error is a subclass of java.lang.Throwable, and we're not required to check for errors, only checked exceptions.