Adding Single Elements: the add() method : HashSet « Collections « Java Tutorial

1. Java Tutorial
2. Collections
3. HashSet

To modify an element in a set, you should remove it, modify it, and then re-add it.

import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;

public class MainClass {

  public static void main(String[] a) {
    String elements[] = { "A", "B", "C", "D", "E" };
    Set set = new HashSet(Arrays.asList(elements));

    set.add("Z");

    System.out.println(set);
  }
}

[Z, D, A, C, B, E]