Question

I am having some trouble understanding classes in Java.

Such as how do you declare "Inputter" in the helper class like this?

public class Helper
{
     public void Helper(String z)
     {
          if(z.length() == 0)
          {
               System.out.println("You can't leave it blank!");
               System.exit(1);
               System.out.println("It's not working... ;(");
          }
     }
     
     public void Inputter(int a)
     {
          // blah blah
     }
}

Would you call it like this?

Helper x = new Inputter();

Please help, and NO this is NOT a homework question.

Thanks,
Smiling

EDIT: Would this be right:

public class Helper
{
     public Helper(String z)
     {
          if(z.length() == 0)
          {
               System.out.println("You can't leave it blank!");
               System.exit(1);
               System.out.println("It's not working... ;(");
          }
     }
     
     public void Inputter(int a)
     {
          // blah blah
     }
}

and declared with:

Helper x = Helper();

Answer 1

Your problem is not with classes, it is with constructors and methods, and the difference between them.

Methods can have any name you like, they must declare a return type (possibly void), and they’re called like this:

ReturnType r = methodName(param1, param2)

Constructors are used to create instances of classes (objects). They must have the same name as the class, they must not have a return type (not even void), and they’re called like this:

MyClass m = new MyClass(param1, param2);

There are several problems in your code:

• Helper has the correct name for a constructor, but because it declares a void return type, the compiler will treat it as a method.
• Inputter doesn’t even have the correct name for a constructor. To use it as a constructor with new, it would have to be part of a class called Inputter

Perhaps you should start out reading the introduction to OO part of the Java tutorial.