Why does this() and super() have to be the first statement in a constructor?

[Tom Ball]

If you have an initialization problem that is difficult to resolve in a
constructor, a common solution is to have a public factory method and a
private constructor.

Tom

On Fri, Oct 7, 2011 at 9:58 AM, Paul Benedict <pbenedict at apache.org> wrote:

> It's a compiler error because the superclass is guaranteed to be
> initialized first before the subclass.
>
> On Fri, Oct 7, 2011 at 11:51 AM, Vimil Saju <vimilsaju at yahoo.com> wrote:
> > If you have subclass then java requires that this() or super has to be
> first statement in the constructor of the subclass.
> > Here is an example
> >
> > publicclassMyClass{
> >         publicMyClass(intx){}
> > }
> >
> > publicclassMySubClassextendsMyClass{
> >         publicMySubClass(inta,intb){
> >                 intc =a +b;
> >                 super(c); // COMPILE ERROR
> >         }
> > }The above compilation error can be resolved by rewriting the code in the
> constructor as follows
> >
> > publicclassMySubClassextendsMyClass{
> >         publicMySubClass(inta,intb){
> >                 super(a + b);
> >         }
> > }Can't the Java compiler detect that in the previous code there was no
> access to the instance fields or methods and therefore allow the code to
> compile without any error.
> >
> >
>
>