/**

The hash table data.
*/
//存放键值对的数组
private transient Entry<?,?>[] table;

/**

The total number of entries in the hash table.
*/
//大小
private transient int count;

/**

The table is rehashed when its size exceeds this threshold. (Thevalue of this field is (int)(capacity * loadFactor).)

@serial
*/
//阀值
private int threshold;

/**

The load factor for the hashtable.

@serial
*/
//负载因子
private float loadFactor;
//默认初始容量为11，负载因子0.75
public Hashtable() {
this(11, 0.75f);
}

//1.8版本没有修改，没有维护红黑树结构
public synchronized V put(K key, V value) {
// Make sure the value is not null
if (value == null) {
throw new NullPointerException();
}

// Makes sure the key is not already in the hashtable.Entry<?,?> tab[] = table;int hash = key.hashCode();//求余获得索引int index = (hash & 0x7FFFFFFF) % tab.length;@SuppressWarnings("unchecked")Entry<K,V> entry = (Entry<K,V>)tab[index];for(; entry != null ; entry = entry.next) { if ((entry.hash == hash) && entry.key.equals(key)) { V old = entry.value; entry.value = value; return old; }}addEntry(hash, key, value, index);return null;

}

/**

Removes the key (and its corresponding value) from thishashtable. This method does nothing if the key is not in the hashtable.@param key the key that needs to be removed@return the value to which the key had been mapped in this hashtable,or <code>null</code> if the key did not have a mapping@throws NullPointerException if the key is <code>null</code>
*/
public synchronized V remove(Object key) {
Entry<?,?> tab[] = table;
int hash = key.hashCode();
int index = (hash & 0x7FFFFFFF) % tab.length;@SuppressWarnings("unchecked")
br/>@SuppressWarnings("unchecked")
for(Entry<K,V> prev = null ; e != null ; prev = e, e = e.next) {
if ((e.hash == hash) && e.key.equals(key)) {
modCount++;
if (prev != null) {
prev.next = e.next;
} else {
tab[index] = e.next;
}
count--;
V oldValue = e.value;
e.value = null;
return oldValue;
}
}
return null;
}