sorting collections with string elements in java

Question

I have a collections...i wrote code to sort values using my own comparator my comparator code is

private static class MatchComparator implements Comparator<xmlparse> {
    @Override
    public int compare(xmlparse object1, xmlparse object2) {
        String match1 = object1.getMatchId();
        String match2 = object2.getMatchId();
        return match1.compareTo(match2);
    }
}

I will call Collections.sort(list,new MatchComparator());

Everything is fine but my problem is the sorted list is wrong when i print it...

Input for list

Match19
Match7
Match12
Match46
Match32

output from the sorted list

Match12
Match19
Match32
Match46
Match7

my expected output is

Match7
Match12
Match19
Match32
Match46

Answer 1

to get the order you need, you could either prefix the 1 digit numbers with zero ( eg Match07 ) or you have to split the string in a prefix and a numeric part, and implement the sorting as numeric comparison

Answer 2

The problem is that String.compareTo(..) compares the words char by char.

If all string start with Match, then you can easily fix this with:

public int compare(xmlparse object1, xmlparse object2) {
    String match1 = object1.getMatchId();
    String match2 = object2.getMatchId();
    return Integer.parseInt(match1.replace("Match"))
         - Integer.parseInt(match2.replace("Match"));
}

In case they don't start all with Match, then you can use regex:

Integer.parseInt(object1.replaceAll("[a-zA-Z]+", ""));

Or

Integer.parseInt(object1.replaceAll("[\p{Alpha}\p{Punch}]+", ""));

And a final note - name your classes with uppercase, camelCase - i.e. XmlParse instead of xmlparse - that's what the convention dictates.