java - null behavior in function overloading with polymorphism -

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• strange java null behavior in method overloading [duplicate] 4 answers
• behavior of method overloading in java [duplicate] 1 answer

i have following code

public class helloworld {      public void printdata (test t) {         system.out.println("reached 1");     }      public void printdata(newtest t) {         system.out.println("reached 2");     }      public static void main(string args[]) {         helloworld h = new helloworld();         h.printdata(null);     } } 

and have 2 simple classes

class test { }  class newtest extends test { } 

and output got reached 2

why second function selected executing , not 1st one? when tried same code making class newtest2 extending test , analogous printdata() function gave me compile time error. there rule select function must executed , when?

why second function selected executing , not 1st one?

because method taking newtest more specific method taking test, , both accessible , applicable.

however, when you've got 2 subclasses of test, neither conversion more specific other, hence call ambiguous.

see jls section 15.12.2.5 exact rules involved:

if more 1 member method both accessible , applicable method invocation, necessary choose 1 provide descriptor run-time method dispatch. java programming language uses rule specific method chosen.

the informal intuition 1 method more specific if invocation handled first method passed on other 1 without compile-time type error.