Are the threads generated by 2 separate executor services in different threads guaranteed to be different?

Question

Lets say I have 2 different threads running concurrently. Each thread spins up a cached thread pool executor service that spins a bunch more threads. Will each pool have their own distinct set of threads? Or is there a possibility for threads to be shared between them?

Answer 1

Will each pool have their own distinct set of threads? Or is there a possibility for threads to be shared between them?

Each pool has control over its own threads -- when to create new ones, when to destroy them etc. No two ThreadPools will ever "see" one another's threads.

In other words: there is no "giant pool" at the JVM level from which ExecutorServices, or ScheduledExecutorServices or even ForkJoinPools would pick from. Were it the case, the maintenance cost would be prohibitive...