为什么Java ThreadLocal变量是静态的(Why should Java ThreadLocal variables be static)

 我在这里读过Threadlocal的JavaDoc 
 
 http://java.sun.com/j2se/1.5.0/docs/api/java/lang/ThreadLocal.html 
 
 并且它说“ThreadLocal实例通常是希望将状态与线程关联的类中的私有静态字段（例如，用户ID或事务ID）。 
 
 但我的问题是为什么他们选择使它静态（通常） - 这让事情有点混乱有“每个线程”的状态，但字段是静态的？ 

I was reading the JavaDoc for Threadlocal here
 
http://java.sun.com/j2se/1.5.0/docs/api/java/lang/ThreadLocal.html
 
and it says "ThreadLocal instances are typically private static fields in classes that wish to associate state with a thread (e.g., a user ID or Transaction ID). "
 
But my question is why did they choose to make it static (typically) - it makes things a bit confusing to have "per thread" state but the fields are static?

原文：https://stackoverflow.com/questions/2784009