Question: My Java program creates a huge number of objects dynamically and even more inside each of them... One thread does some processing and when the user calls a method on the object, it will kill the thread.

After that the object has to be killed so that it can be garbage collected... How do I do it?

Answer: You do not "kill" objects, just stop just keeping any references to them and garbage collector will find all objects that are "dereferenced" and  do the rest...