Java 6: Constructor argument, null and the ternary operator

Question

Just for curiousity...

Assume I have a Class with two constructors:

public Class(){}
public Class(int x){}

and I want to create a new class through with the following statement below:

 new Class( ( true ) ? 100 : null);

Would this be acceptable? Will null instantiate the Class with the empty/default constructor? If not, is there a way to accomplish this with the ternary operator?

Note that I am on Java version 6.

Answer 1

You can do this

Class cl = flag ? new Class(100) : new Class();

By definition, the type of a ? : is the same as the last argument. i.e. Object, you cannot make it type less and value less.

Answer 2

new Class( ( true ) ? 100 : null);

the reason you wont have an empty constructor is because, the only choices we would get would be new Class(100) and new Class(null)

1. new Class(null) 
2. new Class()

Now 1 is not same as 2

null is comprehended as an Object, where as the constructor is expecting a int. If we had

 public Class(Integer x){} 

then new Class(null) would have been allowed since Object is a super class for Integer. Thus the only alternative is

boolean check = true;
check ? new Class(100) : new Class();

Answer 3

You can use variable arguments

Class(int... x){} //constructor

and then use new Class(); or new Class(2);