CODEWITHSUNDEEP
java
A-SM
A-SM

Reputation: 884

How to completely hide superclass method in Java

Recently I'm thinking about making my own Date library. And I'm finding a problem here, here it is:

How do I hide a superclass method in subclass? So it won't be detected in subclass.

Example: I have a class that extends to Date, and another class that extends to the previous class. In my new subclass, it detects all the methods from Date, like getDate etc. What I want is that in my subclass all the methods from Date are undetected, not throwing an exception, but completely undetected.

Thanks in advance :)

Upvotes: 19

Views: 14429

Answers (5)

Vegard
Vegard

Reputation: 1942

You can't hide it if it is extended, but you can override.

if you want your API user to not use the method I suggest a override and just throw this exception:

UnsupportedOperationException

but looking at what you wrote, you should consider making Date a field in your class, not extend the class.

Upvotes: 12

user3911901
user3911901

Reputation: 49

Override the method and make it static, it will hide the method of super class

Upvotes: 0

Tomas Bilka
Tomas Bilka

Reputation: 649

Not possible.

If what you want was possible, then inherintence would be broken. Suddenly, when you use a certain IS-A type of Date, you would not be able to call any Date type methods. This is wrong on several levels. For example, it breaks the Liskov Substitution Principle.

Upvotes: 7

Ravi K Thapliyal
Ravi K Thapliyal

Reputation: 51721

Favour Composition over Inheritance here.

Instead of inheriting a Date have it as a member field inside your MyDate class.

public class MyDate {
    private Date dt = new Date();

    // no getDate() available

    public long getTime() {
        return date.getTime();
    }
}

You get complete control over the Date API that's visible to your subclasses (without the need to throw any exceptions) but this approach is more practical when the methods you want to hide outnumber the ones you want to remain accessible.

Upvotes: 40

stinepike
stinepike

Reputation: 54722

you can use Delegation instead

public class NewDate{
  Date d;
  NewDate(){
     d = new Date();
  }

  methodsYouWantToChange(){
     // new implementation
  }


  methodsYouDontWantToChange(){
     d.methodsYouDontWantToChange();
  }


  newMethods(){
     // new implementation
  }
}

Upvotes: 5

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