Can Java Constructor construct an object of a subclass?

Is there a way to modify the class being constructed in a constructor?

public class A {
  A() {
    //if (condition) return object of type B
    //else return A itself
  }
}
public class B extends A { }

Basically I want to use the base class constructor as a factory method. Is it possible in java?

From stackoverflow

• No, you can't do this.

• No, constructors will only allow a return value of the class they represent. That is why there is no return value specified in the constructor.

  Steve Kuo : Constructors don't return values

• No, you'll have to use a factory method for A if you want to do this. The client of your class has a right to expect that, if he does new A(), he gets an object of class A, and no other.

  : well, this is possible in some other languages. when user does new A() he can as well get subtype of A. So conceptually I see no issue.

  Pavel Minaev : Nonetheless, it is the expectation in Java.

• You could try using reflection to instantiate the subclass. However it is a bad idea because a class shouldn't know about its subclasses.

  Using a factory method is the best approach in your case.

• You cannot do it in a constructor but you could do:

  public class A {
  
  private A(){ }
  
  public static A getInstance(){
       if (condition) 
          return new B();
       else 
          return new A();
  }
  
  }
  
  class B extends A {
  
  }
  

• When constructor code is being invoked the object is already created - you are only initializing its fields. So it's too late to modify class of the object.