Hashtable vs. HashMap

HashMaps accept null values, while Hashtables don't.

import java.util.HashMap;
import java.util.Hashtable;

import junit.framework.TestCase;

public class HashMapTest extends TestCase {
   private HashMap map = new HashMap();
   private Hashtable hashtable = new Hashtable();
  
   public void testHashMap() {
       map.put("name", null);
       assertNotNull(map);
       assertEquals(1,map.size());
   }
  
   public void testHashtable() {
       hashtable.put("name", null);
       assertNotNull(hashtable);
       assertEquals(1,hashtable.size());
   }   
}

The 2nd test simply throws a NullPointerException.

Hashtable is historical, according to JavaPractices.