是否“放入"?覆盖现有值? [英] Does "put" overwrite existing values?

问题描述

哈希表的新问题很简单.出于某种原因，谷歌搜索并没有给我一个直接的答案.假设我已经设置了<int,String>哈希表:

New to hashtables with a simple question. For some reason googling hasn't gotten me a straight answer. Say I've got an <int,String> hashtable set up:

myHashtable.put(1,"bird");
myHashtable.put(2,"iguana");

，我想将"bird"更改为"fish"(并使索引保持不变).我可以只做一个简单的put，还是需要删除该条目，或者什么?

and I want to change "bird" to "fish" (and leave the index the same). Can I just do a simple put, or do I need to delete the entry, or what?

推荐答案

是.

如果已经存在到指定键的映射，则旧值将被替换(并返回).参见 Hashtable.put()

If a mapping to the specified key already exists, the old value will be replaced (and returned). See Hashtable.put().

对于多线程环境，我建议

For multi-threaded environment, I'd recommend ConcurrentHashMap or another ConcurrentMap implementation. Though Hashtable is synchronized, there are more sophisticated implementations available now for concurrent mapping, such as Guava's MapMaker and CacheBuilder.

还请记住，由于不支持基本类型参​​数，Map将具有类型参数<Integer, String>.

Also keep in mind the Map is going to have the type parameters <Integer, String> since primitive type parameters aren't supported.

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