Checking for Existence: the contains() method reports if a specific element is within the set : HashSet « Collections « Java Tutorial

1. Java Tutorial
2. Collections
3. HashSet

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));

    System.out.println(set.contains("A"));
  }
}

true