Dan's Comprehensive Exam #8

[John Hembree]

Question 10

class A {
  void m1() {System.out.print("A.m1");}
}
class B extends A {
  void m1() {System.out.print("B.m1");}
  static void m1(String s) {System.out.print(s+",");}
}
class C {
  public static void main (String[] args) {
    B.m1("main");
    new B().m1();
  }
}

Prints: main,B.m1
Why isn't this a compiler error at B.m1("main");? Is it because they are in the same file and that tells class C where B is? Although m1(String s) is a static method, I didn't think that B was created until new was used on it. Is the compiler doing something for me since the code is asking for B.m1("main");?

[Dan Chisholm]

John,
Welcome to the JavaRanch!
Static methods can be invoked directly on the class: there is no need for an instance of the class. Please note the statement
B.m1("main");
does not make use of a reference to an instance of the class B. Instead, the method is invoke on the class--not on an instance of the class.

[John Hembree]

Thanks, for the response, it started to make more sense to me after I posted it. I started to think about the other static methods that are in your exams like Math.round(0.5f);, I don't have an instance of Math either but I can use the methods.