Java – if multiple threads are updating the same variable, what should be done to update the variable correctly for each thread?

If multiple threads are updating the same variable, what should I do to update the variable correctly for each thread?

Any help would be appreciated

Solution

There are several options:

1) Synchronization is not used at all

This works only if the data is of primitive type (not long / double), and you don't care about reading stale values (which is unlikely)

2) Declare the field volatile

This will ensure that stale values are not read It also applies to objects (assuming that the object will not change after creation) because of the guarantee of volatile variables (see "Java Memory Model")

3) Using Java util. concurrent. Atomiclong, atomicinteger, etc

They are thread safe and support special operations, such as atomic increment and atomic comparison and setting operations

4) Use the same lock to protect read and write

This method provides mutual exclusion, which allows to define a large atomic operation in which multiple data members are manipulated as a single operation