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I was wondering why in java constructors are not inherited? You know when you have a class like this:

public class Super {

  public Super(ServiceA serviceA, ServiceB serviceB, ServiceC serviceC){

    this.serviceA = serviceA;

    //etc

  } 

}

Later when you inherit from Super, java will complain that there is no default constructor defined. The solution is obviously something like:

public class Son extends Super{

  public Son(ServiceA serviceA, ServiceB serviceB, ServiceC serviceC){

    super(serviceA,serviceB,serviceC);

  }

}

This code is repetitive, not DRY and useless (IMHO)... so that brings the question again:

Why java doesn't support constructor inheritance? Is there any benefit in not allowing this inheritance?

1 Answer

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by (46.1k points)

When you inherit from Super this is what in reality happens:

public class Son extends Super{

  // If you dont declare a constructor of any type, adefault one will appear.

  public Son(){

    // If you dont call any other constructor in the first line a call to super() will be placed instead.

    super();

  }

}

So, that is the reason, because you have to call your unique constructor, since"Super" doesn't have a default one.

Now, trying to guess why Java doesn't support constructor inheritance, probably because a constructor only makes sense if it's talking about concrete instances, and you shouldn't be able to create an instance of something when you don't know how it's defined (by polymorphism).

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