java - Which overloaded method will execute and why? -

java - Which overloaded method will execute and why? -

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which overload selected null in java? 3 answers how overloaded methods work? 2 answers public class nulldemo { /** * @param args */ public static void main(string[] args) { // todo auto-generated method stub nulldemo n = new nulldemo(); n.execute(null); } public void execute(object o) { system.out.println("object"); } public void execute(double o) { system.out.println("double"); } }

i have executed above code , execute method execute(double o).i need know reason why executed execute(double o) , not execute(object o)

and suppose

public class nulldemo { /** * @param args */ public static void main(string[] args) { // todo auto-generated method stub nulldemo n = new nulldemo(); n.method1(null); /// give compilation error } public void method1(float o) { system.out.println("object"); } public void method1(double o) { system.out.println("double"); } }

if create method public void method1(float o) , public void method1(double o) give compilation error why so? related hierarchy?

java prefer phone call method furthest downwards inheritance tree. consider next situation:

class demo { public void dosomething(parentclass foo) { //..... } public void dosomething(childclass foo) { //..... } public static void main() { demo demo = new demo(); demo.dosomething(new childclass()); } }

in above situation, method phone call can match either of 2 methods. however, can see intuitively should match sec method.

you can read exact behavior in java spec: http://docs.oracle.com/javase/specs/jls/se8/html/jls-15.html#jls-15.12.2

java oop method-overloading