1.2HashTable

详见&＃xff1a;HashMap-Hash链表结构

HashTable不仅仅继承于Map接口实现了Map的主结构Entry&＃xff0c;而且还是Dictionary的子类。

private static class Entry implements Map.Entry {int hash;final K key;V value;Entry next;protected Entry(int hash, K key, V value, Entry next) {this.hash &＃61; hash;this.key &＃61; key;this.value &＃61; value;this.next &＃61; next;}public V setValue(V value) {//注意&＃xff0c;HashTable的value不可为空if (value &＃61;&＃61; null)throw new NullPointerException();V oldValue &＃61; this.value;this.value &＃61; value;return oldValue;}}

HashTable的内部类Entry&＃xff0c;包括了hash值、key、value和指向下一个Entry的引用。需要注意的是value不能为空。

public class Hashtableextends Dictionaryimplements Map, Cloneable, java.io.Serializableprivate transient Entry[] table; //存储键值对的数组private transient int count; //table中存储的键值对总数private int threshold; //阈值private float loadFactor; //负载因子private transient int modCount &＃61; 0; //用于快速失败/*** 无参构造函数&＃xff0c;hashtable的初始化容量是11&＃xff0c;负载因子是0.75*/public Hashtable() {this(11, 0.75f);} /*** &＃64;param initialCapacity hashtable的初始化容量.*/public Hashtable(int initialCapacity) {this(initialCapacity, 0.75f);}/*** &＃64;param initialCapacity hashtable的初始化容量.* &＃64;param loadFactor 负载因子.*/public Hashtable(int initialCapacity, float loadFactor) {this.loadFactor &＃61; loadFactor;table &＃61; new Entry[initialCapacity];threshold &＃61; (int)Math.min(initialCapacity * loadFactor, MAX_ARRAY_SIZE &＃43; 1);//初始化hash种子initHashSeedAsNeeded(initialCapacity);}public Hashtable(Map t) {this(Math.max(2*t.size(), 11), 0.75f);putAll(t);}} 3、HashTable详解

3.1&＃xff09;关于初始化

jdk1.7中给HashTable也提供了4个构造方法&＃xff0c;四个方法的唯一差别是对参数initialCapacity、loadFactor&＃xff0c;提供了不同的默认值。最终还是调用initHashSeedAsNeeded方法进行hash种子初始化

3.2&＃xff09;关于写操作

3.3&＃xff09;关于读操作

3.4&＃xff09;关于扩容