So i am pretty confused. I read in an article that version 1.7 onwards java has been 'core-aware'

Now question is if I use Thread class, will the threads be parallel or concurrent assuming that its a multi-core system and tasks are fully disjoint, and lets assume only this process is running on the system?

What was the situation before 1.7 version, does that mean java was only concurrent back then? Also tell the same for the ForkJoinPool and ThreadPool (Executor Framework).

Concurrent: Not on the same instant, on same core sequentially i.e. on mercy of Thread Schedular.

Parallel: On the same instant on different cores e.g. 8 threads/4 cores(hyperthreaded).

Thanks a lot in advance

CodePudding user response：

Parallel is concurrent. "Concurrent" means that the effective order in which events from two or more different threads happen is undefined (not counting events like unlocking a mutex that are specifically intended to coordinate the threads.) "Parallel" means, that the threads are using more CPU resources than a single CPU core is able to provide. Threads can't run in parallel without also running concurrently.

What was the situation before 1.7 version

I don't remember what changed with 1.7, but I was using Java from its earliest days, and the language always promised that threads would run concurrently. Whether or not they also were able to run in parallel was outside of the scope of the language spec. It depended on what hardware you were running on, what operating system and version, what JVM and version, etc.