Difference between these 2 ways of finding Random Numbers?

Question

For example, if I were to generate random numbers between 5 and 50, I know I could write the code as either:

ranNum = (int)Math.random()*(50-5+1)+5;

Or

ranNum = Math.round(Math.random()*(50-5))+5;

In terms of the process to generate the random numbers, what is the difference between the two? And which would be faster?

That's the point, they're not. What's the difference though? — chocotella, Jan 17 '16 at 14:48

score 7 · Accepted Answer · answered Jan 17 '16 at 14:46

Speed is not important here.

ranNum = (int)Math.random()*(50-5+1)+5;

This produces a random number between 5 and 50 where each number has an equal chance of occurring.

ranNum = Math.round(Math.random()*(50-5))+5;

This produces a random number between 5 and 50 however 5 and 50 have half the chance of occuring as the others i.e. before ronding the values has to be < 5.5 to get 5 and >= 49.5 to get 50.

Note: neither is the fastest way to generate a random number in a range.

int n = random.nextInt(50 - 5 + 1) + 5;

This is faster because it uses less random bits.

Difference between these 2 ways of finding Random Numbers?

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