java - Get reference to Thread Object from its ID

Question

How can I get reference to a Running Thread if I know the ID associated with that Thread?

e.g.

long threadID = 12342;
Thread thread = (What goes here?) getThreadFromId(threadID); //I know this is totally made up

Answer 1

You have 2 ways to do it. Both are quite simple:

• Old way: get the root thread group you may access Thread.currentThread().getGroup()..getParent() in loop. and call enumerate(Thread[])

• newer (slower though). for (Thread t : Thread.getAllStackTraces().keySet()) if (t.getId()==id)...

The first method has a small problem that due to a bug in ThreadGroup.destroy(), a ThreadGroup may not enumerate anything at all.

The second is slower and has a security flaw, though.