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POSame input different output..time calculation
 

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  1. POSame input different output..time calculation
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    <p>I have a knotty problem to solve. I use System.currentTimeMillis() before a method call and immediately after that since I have to measure the time elapsed beetween those two statements.</p> <pre><code>waitingTime = System.currentTimeMillis(); //starts calculating time bridge.getIn(direction); // tries to enter the bridge waitingTime = System.currentTimeMillis() - waitingTime ;// time elapsed </code></pre> <p>My concern is that I get different result everytime I run the program.</p> <p>I get this (which is perfect):</p> <pre><code>Generated cars going north: 0 Generated cars going south: 2 Waiting time for every single car: ============================================================== A0/South:109ms A1/South:0ms ============================================================== Mean waiting time southbound cars : 54ms </code></pre> <p>Then a few seconds later I run the program again and I get (which is wrong):</p> <pre><code>Generated cars going north: 0 Generated cars going south: 2 Waiting time for every single car: ============================================================== A0/South:0ms A1/South:94ms ============================================================== Mean waiting time southbound cars : 47ms </code></pre> <p>I say this output is wrong since the waiting time for every car should never be less than 100ms.</p> <p>What does actually affect time calculation based on the currentTimeMillis function?</p> <p>why do I get different results?</p> <p>One might wonder: is the input the same every time? I would say yes.. the input parameters </p> <p>are always the same (both examples) but the program uses the Random class to generate a </p> <p>given number of threads.</p> <p>Is that the culprit?</p> <p>A few details abou the program:</p> <p>A bunch of cars going from north to south (viceversa) travel along a two lane road. After a while they reach a bridge. The bridge is one way only and it has limited capacity. A car takes 100ms to go through the bridge. No traffic collision are allowed.</p> <p>Thanks a lot.</p>
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    1. COwaitingTime is an int?
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    2. COPlease show a [SSCCE](http://sscce.org) as the information you have given is not enough to determine what can be the cause of your issue.
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    3. COIf the waiting time should never be < 100, but is == 0, then I would look for a bug in your code rather than a bug in System.currentTimeMillis(). If there is no car on the bridge, why would the waiting time (and not the waiting + crossing time) be different from 0?
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