Abstract class & final class

Question

Which is more correct... Or which is the more preferred way.
abstract class A
  final method1(){}
  final method2(){}
  final method30(){}
}or
final class A
  private A(){}
  method1(){}
  method2(){}
  method3(){}
}My understanding is that both classes cannot be instantiated. The first one requires writing 'final' for EACH method. The second one involves writing a private constructor.

Answer 1

It depends on what you are trying to do. If you are trying to make a class that can be sub-classed but has some methods that cannot be overriden, then "abstract class A" with final methods is the way to go. If you want a class that cannot be sub-classed or instantiated then "final class A" with private constructor is the way to go.
classes cannot be instantiatedOnly true for "final class A" because you made the only constructor private. Not true for the abstract one.// you forgot return values for the methods
abstract class A
  final static /*void*/ method1(){}  // package private
  final static /*void*/ method2(){}  // package private
  final static /*void*/ method30(){} // package private
// this would work
A a = new A(){};
// if I am in the same package as A, then this would work
a.method1();
// or this
public class B extends A
  public B(String whatever)
    // Although, I cannot override the super methods
    // becuase they are all declared as final
    // I can only invoke them if I am in the same package.  You
    // declared them as package private instead of class "private"
}Using final as a class modifier disables the ability to sub-class it but does not disable the ability to create an object of that class. You must make a private constructer. If the only constructor is "private" then you can't subclass or instantiate, so making the class final is uneeded.