Cosntructor question

[Libania Paes]

I know that constructors can�t have a return value. Then I read this question from Osbourne�s Java2 Study Guide:

strictfp class Main{
  public Main(){
  }
  public void Main(){
  }
  strictfp public void Main(double x){
  }
}

I thought it wouldn�t compile because of line 4 and 6 but the book says I�ll compile and run fine because "you can declare a method with the same name as the class name".
So... What�s the difference between constructor and method with the same name as the class name?
Thanks!!!

[Corey McGlone]

Originally posted by Libania Paes:
What�s the difference between constructor and method with the same name as the class name?

You already pointed out the difference. The difference is that a constructor doesn't have a return type. If a method with the same name as the class has no return type, it is a constructor. However, the second you add a return type to it, it becomes a normal method.
Corey

[Nate Johnson]

The method "public void Main" is just another method that can be called. They will try to trick you into thinking it is the constructor on a lot of questions, especially with inheritence questions. Just remember that it will compile and to always look out for return types in constructor signatures...
Hope that helps some.

[Corey McGlone]

Originally posted by Nate Johnson:
The method "public void Main" is just another method that can be called. They will try to trick you into thinking it is the constructor on a lot of questions...

Nate - be sure you know the difference between a constructor and an entry point method (the "main" method). A constructor is a method that has the same name as the class, such as Object or StringBuffer. An entry point method always has the name "main." They are two entirely different beasts.
Corey

[Nate Johnson]

Yeah I understand... I was just quoting part of the code and Main happened to be the name of the class. The point that I wanted to make was that you should watch out for return types, which shouldn't be there, in constuctor declarations on the exam.
Sorry for the confusion.
[ August 02, 2002: Message edited by: Nate Johnson ]

[Libania Paes]

Thanks everybody!
But I�m still confused... How does the code "know" if the method is a constructor or if is just a method with the same name?
And seconde: what�s the point on naming a method the same as the class? When you call it, it�ll be something like Name.name();?

[Corey McGlone]

First of all, the compiler can recognize a constructor by a couple details:
1. The method has the same name as the class.
2. The method has no return type.
If the method meets both of these requirements, it is recognized as a constructor. If either one of the requirements is not met, the method is not a constructor - it is just another method.
Secondly, there probably isn't much use in naming a method the same name as the class (apart from constructors). The key is that you can name a method the same thing as the class. It's not really good practice to do so. It would make your code more confusing because, in general, when people see a method that has the same name as the class, it is presumed that the method is a constructor. When studying for the SCJP, however, you'll encounter many instances in which you need to know what Java can do, not necessarily what you should do with Java.
I hope that helps,
Corey

[Libania Paes]

Prefect!!!
Thanks, now I got it!

[Corey McGlone]

In addition to the requirements I stated, from the JLS:

Unlike methods, a constructor cannot be abstract, static, final, native, strictfp, or synchronized.

Take a look at the JLS, §8.8 Constructor Declarations for more details, including the generic form of a constructor.
Corey

[Libania Paes]

Thanks again!

[Dan Chisholm]

Libania,
One of the new topic specific exams on my mock exam site covers constructors. Please click on the URL in my signature.

[Libania Paes]

Dan,
I took a look at the questions and I liked very much your site. Thanks for the tip!