contains() and containsValue(): check to see if a specific value is found within the Hashtable : Hashtable Basics « Collections « Java Tutorial

1. Java Tutorial
2. Collections
3. Hashtable Basics

public boolean contains(Object value)
public boolean containsValue(Object value)

import java.util.Hashtable;

public class MainClass {
  public static void main(String[] s) {
    Hashtable table = new Hashtable();
    table.put("key1", "value1");
    table.put("key2", "value2");
    table.put("key3", "value3");

    System.out.println(table.contains("value3"));

  }
}

true