How to get feed back from threads? Java

Question

For example, I launched threads 1,2 and 3, how do I keep an eye on the state of the threads? Or how do I get return values from them?

Lets say I have a server class that has threads listen(), I would like to be able to get some values from listen() or vice versa.

Server -> listen().getValue().
listen() get arraylist from server.

Answer 1

使用java.util.concurrent.Future

Answer 2

I believe what you are looking for is called Java IPC (inter process communication) mechanisms. There are plenty. For IPC in a single JVM, you can look into java.util.concurrent package, such as ConcurrentLinkedQueue .