Java final abstract class

Question

I have a quite simple question:

I want to have a Java Class, which provides one public static method, which does something. This is just for encapsulating purposes (to h

Answer 1

Reference: Effective Java 2nd Edition Item 4 "Enforce noninstantiability with a private constructor"

public final class MyClass { //final not required but clearly states intention
    //private default constructor ==> can't be instantiated
    //side effect: class is final because it can't be subclassed:
    //super() can't be called from subclasses
    private MyClass() {
        throw new AssertionError()
    }

    //...
    public static void doSomething() {}
}

Answer 2

No, abstract classes are meant to be extended. Use private constructor, it is not a workaround - it is the way to do it!

Answer 3

You can't mark a class as both abstract and final. They have nearly opposite meanings. An abstract class must be subclassed, whereas a final class must not be subclassed. If you see this combination of abstract and final modifiers, used for a class or method declaration, the code will not compile.