/**
-
The hash table data.
*/
//存放鍵值對的數組
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. (The
- value of this field is (int)(capacity * loadFactor).)
-
@serial
*/
//閥值
private int threshold;/**
- The load factor for the hashtable.
-
@serial
*/
//負載因子
private float loadFactor;
//默認初始容量爲11,負載因子0.75
public Hashtable() {
this(11, 0.75f);
}//1.8版本沒有修改,沒有維護紅黑樹結構
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(); //求餘獲得索引 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 this
- hashtable. 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;br/>@SuppressWarnings("unchecked")
Entry<K,V> e = (Entry<K,V>)tab[index];
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;
}