Have you ever paid attention to those classes in the collection that are thread safe?

In the set framework , Some classes are thread safe , These are all jdk1.1 The emergence of . stay jdk1.2 after , There are lots of non thread safe classes . Here are the classes for thread safe synchronization ：

vector： Just like arraylist There is more synchronization mechanism （ Thread safety ）, Because it's less efficient , It is not recommended now . stay web Application , Especially the front page , Often efficiency （ Page response speed ） It's a priority .

statck： Stack , First in, then out

hashtable： Just like hashmap More thread safety

enumeration： enumeration , Equivalent to iterator

In addition to these , The rest are non thread safe classes and interfaces .