Question

Do you need to call remove on a thread local if you are not deploying in a server environment, even if the app uses a cached thread pool?

public static ThreadLocal<Integer> i = new ThreadLocal<Integer>(){{
    public Integer initialValue(){return 3;}
};

Answer 1

In theory, if both the Thread and ThreadLocal are still in play, the value will be reachable. If either are unreachable, in theory, the value is garbage collectible if otherwise unreferenced. However, there is a bug in OpenJDK which means if the value references the ThreadLocal (surprisingly common) and the Thread is still running, it’ll leak.

So yes, in a sense, there is nothing special about a server environment. However, generally where you are repeated reloading code during development then there it often the case that the ThreadLocal is reachable from the value (value to class-of-the-value to class-loader-of-the-class to all-classes-ever-loaded-through-class-loader to static-fields-of-those-classes to a ThreadLocal). Implementations of Java Beans and JDBC may have similar issues.