I understand that Math.random() by itself generates a random double between 0.0 and 1.0, including 0.0 but excluding 1.0. I also understand that casting to an int truncates everything after the decimal without rounding.
What I don't understand is how something like
System.out.println((int)(Math.random() * 27));
can actually produce a random number from 0 through 26. Since Math.random() by itself only produces 0.0 through 0.9, and 9 * 27 is 24.3, it seems like the greatest int the above code should be able to produce is 24. How does this work?
Through searching for answers to this I have discovered that there are better ways to generate random numbers, but the book I am working through describes this particular method, and I'd like to understand how it works.
The range of Math.random() isn't 0.0 through 0.9, it's 0.0 through the greatest possible double less than 1.0, about 0.9999999999999999 or so.
Returns:
a pseudorandom double greater than or equal to 0.0 and less than 1.0.
If you multiply the largest possible result by 27 and truncate it by casting to int, you will get 26.
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