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/**
-
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. (The
- value 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 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;}
（编辑：李大同）
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