Java TreeMap (comparator) and get method ignoring the comparator

Question

public final Comparator<String> ID_IGN_CASE_COMP = new Comparator<String>() {

        public int compare(String s1, String s2) {
            return s1.compareToIgnoreCase(s2);
        }
    };

private Map< String, Animal > _animals = new TreeMap< String, Animal >(ID_IGN_CASE_COMP);

My problem is, how to use method get(id) ignoring the given comparator. I want the map to be order by Case Insensitive but, I want it to be case sensitive when I fetch the values by a given key.

Answer 1

I think the answer is easy. Implement your own comparator that does a case insensitive sort but does NOT return 0 for "A" and "a"... sort them too.

The issue is that your comparator returns 0 for the compare( "A", "a" ) case which means it is the same key as far as the map is concerned.

Use a comparator like:

public final Comparator<String> ID_IGN_CASE_COMP = new Comparator<String>() {

    public int compare(String s1, String s2) {
        int result = s1.compareToIgnoreCase(s2);
        if( result == 0 )
            result = s1.compareTo(s2);
        return result;
    }
};

Then all keys will go in regardless of case and "a" and "A" will still be sorted together.

In other words, get("a") will give you a different value from get("A")... and they will both show up in keySet() iterators. They will just be sorted together.