This question has to do with the following rule.
Java Language Specification section 8.8.9:
If a class contains no constructor declarations, then a default constructor that takes no parameters is automatically provided:
If the class being declared is the primordial class Object, then the default constructor has an empty body.Otherwise, the default constructor takes no parameters and simply invokes the superclass constructor with no arguments.
A compile-time error occurs if a default constructor is provided by the compiler but the superclass does not have an accessible constructor that takes no arguments.
Now, let's look at your example.
Your class TestSuper has a constructor that takes an int. The compiler will not automatically add a default constructor to class TestSuper, because there is already a constructor in the class.
Your class TestSub does not have a constructor declaration. So the compiler will automatically add a default constructor to class TestSub,
which will invoke TestSuper's no-args constructor.
The problem is in that last part: class TestSuper doesn't have a no-args constructor, so you get an an error.
[ August 19, 2007: Message edited by: Jesper Young ]