There are a number of API's which require the current thread and which will materialize it via Thread::current() if not passed in directly e.g.

HandleMark hm;
ResourceMark rm;
JNIHandles::make_local(obj);

but in many cases we already have the current thread accessible as THREAD and/or thread via *ENTRY wrappers or a TRAPS parameter, which we can pass directly e.g.

HandleMark hm(THREAD);
ResourceMark rm(THREAD);
JNIHandles::make_local(THREAD, obj);