Java Collections Sort not accepting comparator constructor with arg

Question

I'm getting a compiler error for this line:

Collections.sort(terms, new QuerySorter_TFmaxIDF(myInteger));

My customized Comparator is pretty basic; here's the signature and constructor:

public class QuerySorter_TFmaxIDF implements Comparator<Term>{  
private int numberOfDocs;
QuerySorter_TFmaxIDF(int n){
    super();
    numberOfDocs = n;
}

}

Is there an error because I'm passing an argument into the Comparator? I need to pass an argument...

Answer 1

There's no reason you can't pass an argument to that constructor. Your code is missing:

1. The superclass. Your constructor calls super() so I assume there is one; and

2. The compare() method required by the Comparator interface.

What exactly is numberOfDocs meant to do here?

Answer 2

Your Comparator needs to compare Strings because your ArrayList contains Strings.

public class QuerySorter_TFmaxIDF implements Comparator<Term> {  

has to be

public class QuerySorter_TFmaxIDF implements Comparator<String> {  

Answer 3

The problem lies with your comparator. It's for sorting Term-s but the array you're handing it via the Collections.sort() method has elements of type String.