*
*
More formally, if this map contains a mapping from a key
* {@code k} to a value {@code v} such that {@code (key==null k==null :
* key.equals(k))}, then this method returns {@code v}; otherwise
* it returns {@code null}. (There can be at most one such mapping.)
*
*
A return value of {@code null} does not necessarily
* indicate that the map contains no mapping for the key; it's also
* possible that the map explicitly maps the key to {@code null}.
* The {@link #containsKey containsKey} operation may be used to
* distinguish these two cases.
*/
public V get(Object key)
{
Entry
if (e == null)
return null;
e.recordAccess(this);
return e.value;
}
/**
* This method is invoked by the superclass whenever the value
* of a pre-existing entry is read by Map.get or modified by Map.set.
* If the enclosing Map is access-ordered, it moves the entry
* to the end of the list; otherwise, it does nothing.
*/
void recordAccess(HashMap
{
LinkedHashMap
if (lm.accessOrder)
{
lm.modCount++;
remove();
addBefore(lm.header);
}
}
/**
* Removes this entry from the linked list.
*/
private void remove()
{
before.after = after;
after.before = before;
}
这里我们来看一下recordAccess方法！
上面我们不是讲过accessOrder这个参数值控制着LinkedHashMap的迭代顺序嘛，这里我们来看一下。
当accessOrder为true时，remove方法就是将当前元素从双向链表中移除，
addBefore方法再将当前元素插入到链表的头部去，这样最近读到的元素，在迭代的时候是优先被迭代出来的！
这就是所谓的LRU算法（Least Recently Used）：最近最少使用