Java Programming

Hello,

I have come across this line in a piece of code
ThreadLocal<DiagnosticContext> tl= new ThreadLocal<DiagnosticContext>();

Have not come across this kind of statement in any other java code earlier, but i presumed this shld be an associative array declaration.
Google search did not fetch me resources explaining the associative array like above though I believe the same can be achieved via Maps, Arraylist

So my question is
Whether Java is still using the above one for declaring an associative array?
Can someone please explain the syntax of the above statement? ie How to declare an associative array and use it like above one.

Thank you in advance.