Abstract vs No instance approach?

Question

I have one class (class util) for generating password(it has only one public static method ). Here two ways are : To make it abstract so no one can create its instance

public abstract  class PasswordGenerator {

  public static String randomstring(int lo, int hi) {
     // Some logic , doesn't matter 
      return "";
  }
}

or to make its constructor private. So What's the best approach to do that ?

public class PasswordGenerator {

  private PasswordGenerator() {

  }

  public static String randomstring(int lo, int hi) {
    // Some logic , doesn't matter 
    return "";
  }
}

So What's the best approach to do that ?

Possible duplicate of [Static Classes In Java](http://stackoverflow.com/questions/7486012/static-classes-in-java) — Philipp, Jul 13 '16 at 12:07
What you're wanting to do is create a **singleton**. Look for the singleton pattern in Java, or see the answer by @mad_manny — Koos Gadellaa, Jul 13 '16 at 12:28
@KoosGadellaa I disagree, as far as we know the OP doesn't need a singleton because he didn't mention stateful operations. — Spotted, Jul 13 '16 at 13:47

score 3 · Answer 1 · edited May 23 '17 at 12:19

3

You should definitely not make the class abstract, as this might indicate to other developers, that it is intended to be extended (and therefor instantiated).

Having a class technically being able to be instantiated is a minor problem.

But in this SO thread you can see a workaround, that uses a private constructor in combination with making the class final.

edited May 23 '17 at 12:19

Community

1
1

answered Jul 13 '16 at 12:00

mad_manny

1,081
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28

score 1 · Accepted Answer · answered Jul 13 '16 at 13:44

Make both the class final and the constructor private.

With the final keyword you clearly express the intent that the class is not made to be inherited. With the private constructor you clearly express the intent that the class is not made to be instanciated.

public final class PasswordGenerator {

  private PasswordGenerator() {}

  public static String randomstring(int lo, int hi) {
    // Some logic , doesn't matter 
    return "";
  }
}

Abstract vs No instance approach?

2 Answers2