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2.18 Fixing Random to be more random

Juppies 2 by Dr Heinz M. Kabutz

The bug in our shuffle() method was that we wrote

  Random random = new Random(0);

Instead of

  Random random = new Random();

One little number 0 and our game was not properly random anymore. The Random class generates a pseudo-random number sequence. Every time we call nextInt(), it gives us the next number in its sequence. It is surprisingly difficult to get true random numbers from computers. Having a pseudo-random (not true random) number sequence is an approximation that will work well enough in most cases, and is quite fast. The pseudo-random number sequence has to start at some position. By default, it will at some position determined partly by the System.nanoTime(). Every time we start the program, the System.nanoTime() will be a bit different, thus giving us a different start into the sequence.


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