Accessing "main" in package-private class

[Garrett Smith]

When a class is declared w/o a modifier, it can be described as package-private.

class P {
  static void printS1(){System.out.print("P.printS1 ");}
  void printS2() {System.out.print("P.printS2 ");}
  void printS1S2(){printS1();printS2();}
}
class Q extends P {
  static void printS1(){System.out.print("Q.printS1 ");}
  void printS2(){System.out.print("Q.printS2 ");}
  public static void main(String[] args) {
    new Q().printS1S2();
  }
}

What is the result of attempting to compile and run the above program?
a. Prints: P.printS1 P.printS2
b. Prints: P.printS1 Q.printS2
c. Prints: Q.printS1 P.printS2
d. Prints: Q.printS1 Q.printS2
e. Runtime Exception
f. Compiler Error
g. None of the Above

Can someone clarify what it means to "run" the program? It seems that the question should instead be "What happens when Q.main is called."
Really, there's no way to run this from the command line without any auxiliary code.
What is the wording like on the exam? Like this?

[Sam Stoikol]

I'd say that the result will be a runtime error, because of what you just said: it doesn't have a public modifier before the Q class declaration. So when you try to compile and run the code, the compiler will say something like: exception in thread "main" java.lang.NoClassDefFoundError...

[Monisha Talwar]

This is not really an answer, but another question based on your code example.
When I ran Q's main I got
P.printS1
Q.printS2
I was not expecting this result - can someone explain?

[Sridhar Srikanthan]

Originally posted by Garrett Smith:
When a class is declared w/o a modifier, it can be described as package-private.

class P {
  static void printS1(){System.out.print("P.printS1 ");}
  void printS2() {System.out.print("P.printS2 ");}
  void printS1S2(){printS1();printS2();}
}
class Q extends P {
  static void printS1(){System.out.print("Q.printS1 ");}
  void printS2(){System.out.print("Q.printS2 ");}
  public static void main(String[] args) {
    new Q().printS1S2();
  }
}

What is the result of attempting to compile and run the above program?
a. Prints: P.printS1 P.printS2
b. Prints: P.printS1 Q.printS2
c. Prints: Q.printS1 P.printS2
d. Prints: Q.printS1 Q.printS2
e. Runtime Exception
f. Compiler Error
g. None of the Above
<hr></blockquote>
Can someone clarify what it means to "run" the program? It seems that the question should instead be "What happens when Q.main is called."
Really, there's no way to run this from the command line without any auxiliary code.
What is the wording like on the exam? Like this?

Garrett,
When you declare a public class...that means you can only declare one and only one public class.
If you dont declare any class or interface public as in the above code, it is ok to name the file as any of the existing classes. The runtime will check whether there is a main() method in the class whose name is the filename. Otherwise , a runtime exception is thrown.
On the other hand, when you declare a public class, that should be the name of the file in which other classes can exist. and also the public class must have the main method with the required signature to run.
see this code below

  class Hello1 {
public static void main(String [] args) {
System.out.println("Hello1 Class"); //1
}
}
class Hello2 {
public static void main(String [] args) {
System.out.println("Hello2 Class"); //2
}
}
class Hello3 {
public static void main(String [] args) {
System.out.println("Hello3 Class"); //3
}
}

IN the above code, if you name it as Hello1.java, then its main method is run at runtime. If you name it Hello2.java, its main method is run and so on. Play with it and let me know if thats what you wanted to know
Sri

[Garrett Smith]

I'm ok on that now. I thought to run a program's main from the command line, the class had to be coderanch. I don't know why I thought this. I'm having a kind of stupid day today.
As for the other question regarding overriding and hiding, I've been reading §8.4.8.4 and 8.5.8.5 of the JLS.
Try this thread:
http://java.sun.com/docs/books/jls/second_edition/html/jTOC.doc.html
https://coderanch.com/t/370632/java/java/static-methods-do-not-participate

[Sridhar Srikanthan]

Garrett,
i thought only public class was the problem...Otherwise, I would have given an example of overriding and hiding(static methods are hidden not overridden)
And thats a very important point to note when you are appearing for the exam... because I did get a question testing those concepts
Sri

[Monisha Talwar]

Thanks Garrett,
Both the links u sent were awesome...I think I've understood the concept now.
http://java.sun.com/docs/books/jls/second_edition/html/jTOC.doc.html
https://coderanch.com/t/370632/java/java/static-methods-do-not-participate
--------------------

[Sam Stoikol]

Ups! I think I was wrong, sorry but this was my first time posting a message here. I'll be more careful next time, especially because I need to pass the test next week.