Add elements to a TreeSet « TreeSet « Set « Collections

Return	Method	Summary
boolean	add(E e)	Adds the specified element to this set if it is not already present.
boolean	addAll(Collection<? extends E> c)	Adds all of the elements in the specified collection to this set.


  import java.util.TreeSet;

public class Main {
    public static void main(String args[]) {
        TreeSet<String> ts = new TreeSet<String>();

        ts.add("C");
        ts.add("A");
        ts.add("B");
        ts.add("E");
        ts.add("F");
        ts.add("java2s.com");

        System.out.println(ts);
    }
}


[A, B, C, E, F, java2s.com]


  import java.util.Arrays;
import java.util.TreeSet;

public class Main {
  public static void main(String args[]) throws Exception {

    String elements[] = { "java2s.com", "C", "D", "G", "F" };
    TreeSet<String> set = new TreeSet<String>(Arrays.asList(elements));

    System.out.println(set.headSet("D"));
    System.out.println(set.tailSet(""));
  }
}


[C]
[C, D, F, G, java2s.com]


  import java.util.Comparator;
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.compareTo(aStr);
    }
}

public class Main{
    public static void main(String args[]) {
        TreeSet<String> ts = new TreeSet<String>(new MyComparator());

        ts.add("java2s.com");
        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();
    }
}


java2s.com F E D B A


  import java.util.Collections;
import java.util.Set;
import java.util.TreeSet;

public class Main {
  public static void main(String args[]) throws Exception {
    String elements[] = { "java2s.com", "C", "D", "G", "F" };
    Set<String> set = new TreeSet<String>(Collections.reverseOrder());
    for (int i = 0, n = elements.length; i < n; i++) {
      set.add(elements[i]);
    }
    System.out.println(set);
  }
}


[java2s.com, G, F, D, C]