Java by API/java.util/Comparator

implements Comparator < E >

/**
 *Output: 
 F E D C B A 
  */
import java.util.ruparator;
import java.util.TreeSet;
class MyComparator implements Comparator<String> {
  public int compare(String a, String b) {
    String aStr, bStr;
    aStr = a;
    bStr = b;
    return bStr.rupareTo(aStr);
  }
  // No need to override equals.
}
public class MainClass {
  public static void main(String args[]) {
    TreeSet<String> ts = new TreeSet<String>(new MyComparator());
    ts.add("C");
    ts.add("A");
    ts.add("B");
    ts.add("E");
    ts.add("F");
    ts.add("D");
    for (String element : ts)
      System.out.print(element + " ");
    System.out.println();
  }
}