import java.util.TreeSet; public class Main { public static void main(String[] args) { TreeSet<String> tSet = new TreeSet<String>(); tSet.add("1"); tSet.add("2"); tSet.add("3"); tSet.add("4"); tSet.add("5"); boolean blnExists = tSet.contains("3"); System.out.println("3 exists in TreeSet ? : " + blnExists); } }