When to use Abstract Class?

What is an Abstract class?

In Layman terms: An incomplete class is called an Abstract class.

When to use?

An abstract class is best suited for the scenarios where there is a lot of reusable code which you don’t want to write again and again + There are a few things which are specific to each class.

ie Common things + Uncommon things = Abstract class

Example?

Ceremony:

Common things: Sing Anthem, Hoist Flag, etc.
Specific things: Indian Flag, Indian anthem(For India), China Flag, China anthem(For China), etc.

Sample Code?

Abstract class:

public abstract class BaseCeremony{

    Flag natonalFlag;
    Anthem anthem;

    //**** Common Task ******//
    public void startCeremony(){
        configure();
        hoistFlag();
        singAnthem();
    }

    public void hoistFlag(){
        natonalFlag.hoist();                       
    }

    public void singAnthem(){
        anthem.anthem();                       
    }

    private void configure(){
        natonalFlag = provideFlag();
        anthem = provideAnthem();
    }

    //**** Differs in all part ******//
    public abstract Flag provideFlag();
    public abstract Anthem provideAnthem();

}

Implementation:

public class IndianCeremony extends BaseCeremony{

       public Flag provideFlag(){
            return new IndianFlag();
       }

       public Anthem provideAnthem(){
            return new IndianAnthem();
       }
}

Extra points: Just for you

• An abstract class is an incomplete class that is why you can not create its objects.
• An abstract class should have at least one abstract method to qualify as an abstract class
• Example of abstract class implementation in Android

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