Java Concurrency

Just oracle java tutorials notes

why we need concurrency?

Computer users take it for granted that their systems can do more than one thing at a time

why threads need to communicate with each other?

Computer always run on single core,and they need to share message among threads or processes.

what’s the meaning of thread invoking?

Maybe just create a new thread…Maybe invoke thread is a generalized concept .it concludes create a new thread

why I need to store and use my code arsenal frequently？

Most of my question need to do experiment and I really require it.

how to create thread to count number and sleep 1s?