Why this is compile time error

[Chiranjeevi Kanthraj]

Hi all

if i have a method like

void someMethod(String a)
void someMethod(Object a)

i can call someMethod(null)

But if i have the

void someMethod(String a)
void someMethod(StringBuffer a)

i cant call someMethod(null) which gives compile time error


Please explain why?
Thanks

[Ernest Friedman-Hill]

The compiler will choose the "most specific" method. Because String is a subclass of Object, there's a clear choice between the first two methods; a subclass is deemed to be "more specific" than the superclass. But in your second example, String and StringBuffer are both subclasses of Object, so neither is more specific than the other; there's no clear choice, so it's a compile-time error.