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2.23 Fixing the Integer Swapping Code

Juppies 2 by Dr Heinz M. Kabutz

We were too much in a hurry to enter the code, taking shortcuts and not being careful about each step. This happens frequently when we are overconfident. The first line with indexes[i] += indexes[swap] is correct. However, the second line is wrong. In our example, we wrote y = x - y, but that is not equivalent to y -= x. Our code should have been indexes[swap] = indexes[i] - indexes[swap].

We run the test and it passes this time. Fantastic! Keep the test green to keep the code clean. We have also improved our unit test to confirm that the numbers in the shuffled index are exactly the same as before.

We commit our changes to our local repository, describing our improvements, such as better tests, improved swapping algorithm and having set up NetBeans to automatically run our unit tests every time we run our game. We could submit our changes individually as separate commits or as one, but we should take care that every commit by itself does not break the build.

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Heinz Kabutz Java Conference Speaker

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