[英]Why is ConcurrentNavigableMap implemented as a skip list?
最近我碰到ConcurrentSkipListMap ,这是一个skip list
实现ConcurrentNavigableMap
。 现在,我想知道为什么将它实现为skip list
。
skip list
是否skip list
并发可导航地图的“标准”实现? 是什么让skip list
特别有用呢?
ConcurrentSkipListMap
源代码已记录了原因。
采用此方法而不是通常基于数组的方法有两个原因
这是javadoc
/*
* This class implements a tree-like two-dimensionally linked skip
* list in which the index levels are represented in separate
* nodes from the base nodes holding data. **There are two reasons
* for taking this approach instead of the usual array-based**
* structure: 1) Array based implementations seem to encounter
* more complexity and overhead 2) We can use cheaper algorithms
* for the heavily-traversed index lists than can be used for the
* base lists. Here's a picture of some of the basics for a
* possible list with 2 levels of index:
*
* Head nodes Index nodes
* +-+ right +-+ +-+
* |2|---------------->| |--------------------->| |->null
* +-+ +-+ +-+
* | down | |
* v v v
* +-+ +-+ +-+ +-+ +-+ +-+
* |1|----------->| |->| |------>| |----------->| |------>| |->null
* +-+ +-+ +-+ +-+ +-+ +-+
* v | | | | |
* Nodes next v v v v v
* +-+ +-+ +-+ +-+ +-+ +-+ +-+ +-+ +-+ +-+ +-+ +-+
* | |->|A|->|B|->|C|->|D|->|E|->|F|->|G|->|H|->|I|->|J|->|K|->null
* +-+ +-+ +-+ +-+ +-+ +-+ +-+ +-+ +-+ +-+ +-+ +-+
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