Constructor requiring many input arguments

Question

My question concerns constructors in java. I've learnt that we should minimize the number of arguments to method including constructor. So if I have a class with requires a lot of input arguments to be created how do I best go about this. Should I

A) Include them all in the constructor method signature:

Example:

public MyClass(SomeThing A, Vector v, OtherThing B, int number.. etc.){
      // construct
}

..

MyClass c= new MyClass(..);

c.doSomethingWithAllYouGot();

B) Can I construct only very little and then require the object user to add things before calling specific methods

public MyClass(SomeThing A){
      // construct
}

..

MyClass c=new MyClass(A);

c.attributeVector(v);
c.connectTo(B);
c.setNumber(n);
// etc.

c.doSomethingWithAllYouGot();

The second variant seems more elegant and clean but allows for more errors if the class is incorrectly used.

Or is there a problem with the the design of the class if it has too many input arguments?

Answer 1

If there are really that many parameters, it could that your class is trying to be too many things at the same time. Take this as a hint that it could be broken down into smaller classes.

Alternatively, you could make the constructor package private, and use a builder in the same package to instantiate it.