record< K,V>中使用recordAccess(this)类 [英] Use of recordAccess(this) in Entry<K, V> class
问题描述
/ **
*在HashMap类中查看时,我遇到了这个方法:只要在HashMap中已经存在
*的键k对put(k,v)的调用覆盖了条目中的值
*,就会调用此方法。
* /
void recordAccess(HashMap< K,V> m){
}
实际上,这个方法是在 Entry的内部类中定义的
我无法评论这个评论。这种方法做什么?
PS:我也可以看到这个方法在HashMap的putForNullKey()方法中被调用。 (Entry< K,V> e = table [0]; e!= null; e = e.next){
if($($))$ private $ V putForNullKey(V value){
e.key == null){
V oldValue = e.value;
e.value = value;
e.recordAccess(this); //调用
返回oldValue;
}
}
modCount ++;
addEntry(0,null,value,0);
返回null;
}
更新:我更新了第一个代码片段。
一个LinkedHashMap可以有两个顺序:插入顺序或访问顺序。如果使用访问顺序,则此方法可确保访问的条目移至列表的开头。
While having a look inside HashMap class, I came across this method :-
/**
* This method is invoked whenever the value in an entry is
* overwritten by an invocation of put(k,v) for a key k that's already
* in the HashMap.
*/
void recordAccess(HashMap<K,V> m) {
}
Actually, this method is defined inside the inner class of Entry<K, V>
I'm not able to make out of that comment. What does this method do ?
PS : I can also see this method being called inside's HashMap's putForNullKey() method
private V putForNullKey(V value) {
for (Entry<K,V> e = table[0]; e != null; e = e.next) {
if (e.key == null) {
V oldValue = e.value;
e.value = value;
e.recordAccess(this); // call
return oldValue;
}
}
modCount++;
addEntry(0, null, value, 0);
return null;
}
UPDATE : I've updated the first code snippet.
A LinkedHashMap can have two orders: insertion order, or access order. If access order is used, this method makes sure that the accessed entry is moved to the beginning of the list.
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