How do I make sure thread-safe?

Question

There are basically four ways to make variable access safe in shared-memory concurrency: Confinement. Don't share the variable between threads. . Immutability. Make the shared data immutable. . Threadsafe data type. . Synchronization.

How do you ensure thread-safety?

The best way to achieve thread safety is to avoid shared state. For the state, you need to share you can either use message parsing together with immutable classes or the concurrent data structures together with synchronized blocks and volatile fields.

How do you know if thread-safe?

To test if the combination of two methods, a and b, is thread-safe, call them from two different threads. Put the complete test in a while loop iterating over all thread interleavings with the help from the class AllInterleavings from vmlens. Test if the result is either an after b or b after a.

How do you make a class thread-safe?

To make these classes thread-safe, you must prevent concurrent access to the internal state of an instance by more than one thread. Because Java was designed with threads in mind, the language provides the synchronized modifier, which does just that.

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