import java.util.TreeSet;

/*
 *  Example of TreeSet() Constructor.
 */
public class TreeSetExample
{
    public static void main( String[] args )
    {

        /*
         * Constructs a new, empty tree set, sorted according to the natural
         * ordering of its elements. All elements inserted into the set must
         * implement the Comparable interface.
         * 
         * Furthermore, all such elements must be mutually comparable:
         * e1.compareTo(e2) must not throw a ClassCastException for any elements
         * e1 and e2 in the set.
         * 
         * If the user attempts to add an element to the set that violates this
         * constraint (for example, the user attempts to add a string element to
         * a set whose elements are integers), the add call will throw a
         * ClassCastException.
         */
        TreeSet<String> treeSet = new TreeSet<String>();

        treeSet.add("B");
        treeSet.add("C");
        treeSet.add("A");
        treeSet.add("D");
        treeSet.add("E");

        System.out.println("treeSet : " + treeSet + "\n");

    }
}