interface as a method parameter in Java

Question

I had an interview days ago and was thrown a question like this.

Q: Reverse a linked list. Following code is given:

public class ReverseList { 
    i         


        

Answer 1

The argument needs an object, which class implements an interface (the parameter).

In pseudo Java the code:

void reverse(NodeList node) {
    // your code
}

is equal to:

reverse(x) {
    if(x == null || x instanceof NodeList) {
         // your code
    }else throw new RuntimeException("Some sort of error.");
}

Note; read more on Interfaces here: http://java.sun.com/docs/books/tutorial/java/IandI/interfaceAsType.html