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Read/write conflicts
Another kind of misbehavior that may be exhibited in a multithreaded environment by instances of this RGBColor class is read/write conflicts. This kind of conflict arises when an object's state is read and used while in a temporarily invalid state due to the unfinished work of another thread.

For example, note that during the blue thread's execution of the setColor() method above, the object at one point finds itself in the temporarily invalid state of black. Here, black is a temporarily invalid state because:

1. It is temporary: Eventually, the blue thread intends to set the color to blue.

2. It is invalid: No one asked for a black RGBColor object. The blue thread is supposed to turn a green object into blue.

If the blue thread is preempted at the moment the object represents black by a thread that invokes getColor() on the same object, that second thread would observe the RGBColor object's value to be black.

Here's a table that shows a sequence of events that could lead to just such a read/write conflict:

As you can see from this table, the trouble begins when the blue thread is interrupted when it has only partially finished painting the object blue. At this point the object is in a temporarily invalid state of black, which is exactly what the red thread sees when it invokes getColor() on the object.