The method contains() of Hashtable returns true if the value you are looking for is in the Hashtable collection, otherwise it returns a false.

import java.util.Hashtable; 

public class Main {
 public static void main(String[] args) {
 Hashtable< String, String> ht = new Hashtable< String, String> (); 

 ht.put("1", "one"); 
 ht.put("2", "two"); 
 ht.put("3", "three"); 

 boolean b = ht.contains("three"); 
 System.out.println("Does the value three exist in Hashtable?: " + b); 
 }
}

Runtime:

The value three exists in Hashtable? :true