Hashtable 和 HashMap 的区别

public class Hashtable<K,V> extends Dictionary<K,V>
    implements Map<K,V>, Cloneable, java.io.Serializable
 
public class HashMap<K,V>extends AbstractMap<K,V> implements Map<K,V>, Cloneable, Serializable

1 java.lang.Objecct
2   java.util.Dictionary<K,V>
3     java.util.Hashtable<Object,Object>
4       java.util.Properties