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POHow to follow the origin of a value in Java?
 

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  1. POHow to follow the origin of a value in Java?
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    <p>I have a variable that very rarely gets an incorrect value. Since the system is quite complex I'm having trouble tracing all the code paths that value goes through - there are multiple threads involved, it can be saved and then loaded from a DB and so on. I'm going to try to use a code graph generator to see if I can spot the problem by looking at the ways the setter can be called, by may be there's some other technique. Perhaps wrapping the value with a class that traces the places and changes it goes through? I'm not sure the question is clear enough, but I'd appreciate input from somebody who encountered such a situation.</p> <p>[Edit] The problem is not easily reproducible and I can't catch it in a debugger. I'm looking for a static analysis or logging technique to help track down the issue.</p> <p>[Edit 2] Just to make things clearer, the value I'm talking about is a timestamp represented as the number of milliseconds from the Unix epoch (01/01/1970) in a 64-bit long variable. At some unknown point the top 32 bits of the value are truncated generating completely incorrect (and unrecoverable) timestamps.</p> <p>[Edit 3] OK, thanks to some of your suggestions and to a couple of hours of pouring through the code, I found the culprit. The millisecond-based timestamp was converted into a second-based timestamp by dividing it by 1000 and stored in an <code>int</code> variable. At a later point in code, the second-based timestamp (an <code>int</code>) was multiplied by 1000 and stored into a new <code>long</code> variable. Since both 1000 and the second-based timestamps were <code>int</code> values, the result of the multiplication was truncated before being converted to long. This was a subtle one, thanks to everyone who helped.</p>
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      1. POHow to follow the origin of a value in Java?
      1. USAdam Paynter
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    1. CONasty. Good you found it.
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      1. USThorbjørn Ravn Andersen
 

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