How to make constructor that takes in 2 if there are 2 parameters, or 3 if there are 3

as its instance variables. If I had certain data that had only firstName and lastName, no middleInitial, how would I make the constructor so that it took only 2 parameters instead of three?

asked Jul 20, 2011 at 18:49 41 1 1 gold badge 1 1 silver badge 2 2 bronze badges

9 Answers 9

You simply write a constructor with two parameters and a constructor with three

public YourClass(String firstName, String lastName) < . >public YourClass(String firstName, String middleInitial, String lastName)

Callers can then choose to use the appropriate constructor based on their needs.

answered Jul 20, 2011 at 18:51 140k 66 66 gold badges 284 284 silver badges 349 349 bronze badges

Well, two options:

Just have a constructor with three parameters, and call it using null or the empty string for middleInitial
Overload the constructors, possibly calling one from the other.

As an example for the latter, using an empty string as the default middle initial:

public Person(String firstName, String middleInitial, String lastName) < this.firstName = firstName; this.middleInitial = middleInitial; this.lastName = lastName; >public Person(String firstName, String lastName)

However, the compiler will need to know which one you're calling from the call site. So you can do:

new Person("Jon", "L", "Skeet");

new Person("Jon", "Skeet");

. but you can't do:

// Invalid new Person(firstName, gotMiddleInitial ? middleInitial : . lastName);

and expect the compiler to decide to use the "two name" variant instead.