Sorting a Hashmap's values with sorted Set

Question

I have a hashmap with values that both contain and do not contain asterisks (* ). I want to sort my values so that all values with an (* ) come last. I tried using this line of code:

    SortedSet<String> orderedValues = new TreeSet<String>(myHashMap.values());

but it orders it alphabetically then withing that places all values with an (*) first. is there anyway to reverse that???

Answer 1

you have to write your own java.util.Comparator to do customized sorting. Default String sorting is alphabetical.

EDITED to meet new requirements to group sorting by no asterisks, then all with 1 then all with 2 etc

If you want to group sorting by no asterisks, then all with 1 then all with 2 etc and then inside each grouping, sort alphabetically, then you probably want something like this:

public class AsterisksLast implements Comparator<String>{

@Override
public int compare(String o1, String o2) {


    int numAsterisksInO1 = numberOfAsterisksIn(o1);
    int numAsterisksInO2 = numberOfAsterisksIn(o2);

    if(numAsterisksInO1 == numAsterisksInO2){
        //both contain same number of asterisks
        //(which may be 0)
        //sort 
        //alphabetically
        return o1.compareTo(o2);
    }
    //different number of asterisks sort by fewest
    return Integer.compare(numAsterisksInO1, numAsterisksInO2);

}

private int numberOfAsterisksIn(String s){
    char[] chars =s.toCharArray();
    int count=0;
    for(int i=0; i<chars.length; i++){
        if(chars[i] == '*'){
            count++;
        }
    }
    return count;
}

}

then you need to give it to your TreeSet

SortedSet<String> orderedValues = new TreeSet<String>(new AsterisksLast());
orderedValues.addAll(myHashMap.values());