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Semantics of volatile do not guarantee the atomicity of compound operations that involve read-modify-write sequences such as incrementing a value. See CON01CON02-J. Ensure that compound operations on shared variables are atomic for more information.
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CON25-EX1: If all reads and writes of 64-bit long and double values occur within a synchronized region, the atomicity of the read/write is guaranteed. This requires that no unsynchronized methods in the class expose the value and that the value is inaccessible (directly or indirectly) from other code. (For more information, see CON01CON02-J. Ensure that compound operations on shared variables are atomic.)
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