If more than one thread can access a field should it be marked as volatile?

Question

Reading a few threads (common concurrency problems, volatile keyword, memory model) I\'m confused about concurrency issues in Java.

I have a lot of fields that are acces

Answer 1

The short answer is no. Threading issues require more thought and planning than this. See this for some limitations on when volatile helps for threading and when it does not. The modification of the values has to be properly synchronized, but very typically modification requires the state of more than one variable at a time. Say for example you have variable and you want to change it if it meets a criteria. The read from the array and the write to the array are different instructions, and need to be synchronized together. Volatile is not enough.

Consider also the case where the variable references a mutable object (say an array or a Collection), then interacting with that object will not be thread safe just because the reference is volatile.