Question

I have the following code :

public class Main {
     public void method(Object o)
     {
           System.out.println("Object Version");
     }
     public void method(String s)
     {
          System.out.println("String Version");
     }
     public static void main(String args[])
     {
           Main question = new Main();
           question.method(null);//1
     }
}

why is the result is “String Version” ? and why there is a compiler error if the first method takes a StringBuffer object ?
Another case : if the first method takes a StringBuffer object and I write question.method("word");the result will be “String Version” . Why ? why there is no compiler error ?

Answer 1

The JAVA spec says that in cases like this, the most specific function will be called. Since String is a sub type of Object – the second method will be called.
If you change Object to StringBuffer – there is no specific method since StringBuffer is not a sub type of String and vice versa. In this case the compiler does not know which method to call – hence the error.