Question

the documentations always deals very explicitly with the issues of using one instance of an object with more than one thread.

However what do I need to know when there are some threads that have their own instance at the same time? Which interference could occur? How do I handle members like SimpleDateFormat that are quiet expensive to create?

Thanks
Mike
[;-)

Answer 1

If code from each thread is accessing different instances (objects) of the same class, that is not a problem; unless, of course, those objects are accessing shared objects, such as class static objects.

As the documentation for SimpleDateFormat states:

Date formats are not synchronized. It is recommended to create separate format instances for each thread. If multiple threads access a format concurrently, it must be synchronized externally.

One way of keeping separate instances for each thread would be to use a ThreadLocal object to keep track of separate instances.