Question

I’m learning threads yet, but don’t know much things.

I see that I need implement the Runnable interface and create various instances of the same class to each thread execute each one. It’s correct?

If is correct, I need to create another class to contains the variables that will be accessed/shared by all threads?

EDIT: I need maintain some variables to coordinate the thread work, otherwise they will execute the same work. This will be one variable shared by all threads.

EDIT 2: this questions is related to this: How I make result of SQL querys with LIMIT different in each query? . I will need maintain the quantity of threads that have done a query to database to set the OFFSET parameter.

Answer 1

Each thread needs an instance of a Runnable to do its work, yes. In some cases the threads could share the same instance, but only if there is no state held within the instance that needs to differ between threads. Generally you will want different instances in each thread.

Threads should share as little state as possible to avoid problems, but if you do want to share state, in general you are right that you will need an instance or instances somewhere to hold that state.

Note that this shared state could also be held in class variables rather than instance variables.