when overload same method display(String s ) and display(Object o) ,when pass null in method from main method why display(String s ) is called?

Question

package polymorphism;
/*
 * @author Rahul Tripathi
 */
public class OverLoadingTest {

    /**
     * @param args
     * @return 
     */
    static void display(String s){
        System.out.println("Print String"); 
    }

    static void display(Object s){
        System.out.println("Print Object");                 
    }

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        OverLoadingTest.display(null);
    }

}

Output:

Print String

IN above program when overload same method display(String s ) and display(Object o) ,when pass null in method from main method why display(String s ) is called only. Why not called display(Object o)?

I am actually surprised it compiles rather than say "ambiguous method call". — EpicPandaForce, Aug 27 '14 at 07:18
IT is compiled code.IT will not say ambiguous method call.Please check it. — Rahul Tripathi, Aug 27 '14 at 07:22
possible duplicate of [Java method dispatch with null argument](http://stackoverflow.com/questions/377203/java-method-dispatch-with-null-argument) — ApproachingDarknessFish, Aug 27 '14 at 07:23
possible duplicate of [Overloading with Short and int](http://stackoverflow.com/questions/6268157/overloading-with-short-and-int) — Narmer, Aug 27 '14 at 07:24

Juned Ahsan · Answer 1 · 2014-08-27T07:21:39.093

2

Overloaded method is called on the basis of best/closest match. Object is the top level class, which means this will be matched at the last. So matching starts with the method taking String parameter, as string can be null so it is matched and called.

edited Aug 27 '14 at 07:21

answered Aug 27 '14 at 07:13

Juned Ahsan

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score 1 · Answer 2 · answered Aug 27 '14 at 07:13

The most non-generic method among the matching methods will be selected. i.e, null can be accepted as both Object as well as a String but Since String is also an Object, the compiler thinks that String has a higher probability of being null rather than an Object.

score 0 · Answer 3 · answered Aug 27 '14 at 07:44

0

Because overloadding will be happen with best closet match that is string and object is last closet one because all classes which are inherited from java.lang.object right, so that why it is happen

answered Aug 27 '14 at 07:44

Nageshwararao

1
2

score 0 · Answer 4 · answered Jul 15 '17 at 01:42

In java when multiple overloaded methods are present, java looks for the closest match first. It tries to find the following:

Exact math by type
Matching a superclass type
Converting to a larger primitive type
Converting to an autoboxed type

So in your overloaded method String class is closets sub class of object class.

when overload same method display(String s ) and display(Object o) ,when pass null in method from main method why display(String s ) is called?

4 Answers4