Hashtable 线程安全的,但效率低 内部有上锁的控制 synchronized Hashmap 线程不安全的,但效率高 ConcurrentHashMap 兼顾了线程安全和效率的问题 分析:HashTable锁了整段数据(用户操作是不同的数据段,依然需要等待) 解决方案:把数据分段,执行分段锁(分离锁... ...
java集合04 - map/hashmap/linkedhashmap Map Map实现类的结构及特点 Map:双列数据,存储key-value对的数据 |--- HashMap:作为Map的主要实现类:线程不安全,效率高;可以存储null的key和value |--- TreeMap:保证按照添加的key-value对进行排序,实现排序遍历,此时考虑key的自然排序或定制排序。底层使用的是红黑...
Hashtable is synchronized, in contrast to HashMap. This gives us the reason that HashMap should be used if it is thread-safe, since Hashtable has overhead for synchronization. 2. HashMap If key of the HashMap is self-defined objects, then equals() and hashCode() contract need to be f...
This implementation spares its clients from the unspecified, generally chaotic ordering provided byConcurrentHashMapand Hashtable, without incurring the increased cost associated with TreeMap. It can be used to produce a copy of a map that has the same order as the original, regardless of the ori...
LinkedHashMap preserves the insertion order Hashtable is synchronized, in contrast to HashMap. This gives us the reason that HashMap should be used if it is thread-safe, since Hashtable has overhead for synchronization. 2. HashMap If key of the HashMap is self-defined objects, then equals...