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Categories / Java Tutorial / Collections
 

Creating a TreeSet

The first two constructors create empty tree sets: public TreeSet() public TreeSet(Comparator comp) Pass along a custom Comparator to the constructor that will be used to keep elements ordered. Once the TreeSet is created, you cannot change the comparator. import java.util.Collections; import java.util.Set; import java.util.TreeSet; public class MainClass {   public static void main(String args[]) throws Exception {     String elements[] = { "A", "C", "D", "G", "F" };     Set set = new TreeSet(Collections.reverseOrder());     for (int i = 0, n = elements.length; i < n; i++) {       set.add(elements[i]);     }     System.out.println(set);     System.out.println(((TreeSet) set).comparator());   } } [G, F, D, C, A] java.util.Collections$ReverseComparator@192d342