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CON00-J. Ensure visibility when accessing shared primitive variables
CON01-J. Do not assume Ensure that composite operations on shared variables are atomic
CON02-J. Always synchronize on the appropriate object
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Declaring shared variables as volatile ensures visibility and limits reordering of accesses. Volatile accesses do not guarantee the atomicity of composite operations such as incrementing a variable. Consequently, volatile is not applicable in cases where the atomicity of composite operations must be guaranteed (see CON01-J. Do not assume Ensure that composite operations on shared variables are atomic).
Declaring variables as volatile establishes a happens-before relationship such that a write to the volatile variable is always seen by a subsequent read. Statements that occur before the write to the volatile field also happen-before the read of the volatile field.
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