ThreadLocal & Memory Leak

Question

It is mentioned at multiple posts: improper use of ThreadLocal causes Memory Leak. I am struggling to understand how Memory Leak would happen using Thread

Answer 1

There is nothing inherently wrong with thread locals: They do not cause memory leaks. They are not slow. They are more local than their non-thread-local counterparts (i.e., they have better information hiding properties). They can be misused, of course, but so can most other programming tools…

Refer to this link by Joshua Bloch