To generate a random number in a given range, we can write:
Random().nextInt((max - min) + 1) + min.
I would like to know that is it equal to Random().nextInt(max + 1) - min OR not.
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That is two random generators, how can they be equal?Vishwa Ratna– Vishwa Ratna2020-01-13 07:22:56 +00:00Commented Jan 13, 2020 at 7:22
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1the range of the first one is [min, max], the second, [-min, max - min]. So, no.njzk2– njzk22020-01-13 07:50:01 +00:00Commented Jan 13, 2020 at 7:50
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3 Answers
It's not, just check the edge cases.
For min = 5 and max = 10
max - min + 1 = 6, so nextInt((max - min) + 1) results in minRand = 0 to maxRand = 5. Add min and you get a number between 5 and 10.
max + 1 = 11, so nextInt(max + 1) results in minRand = 0 to maxRand = 10. Substract min and you get a number between -5 and 5.
Comments
It's not, but it seems not easy to explain.
(max - min) + 1 is the argument to nexInt method. It is the value from 0 to the total of elements in that range (from min to max) and then this range is moved to start at the minimum value.
In other words, nextInt((max - min) + 1) generates a random int from 0 to max-min. And adding min will result in a random integer from min to max.
The other expression is just wrong because from 0 to max + 1 doesn't get the range of values you want.
Comments
I would like to know that is it equal to Random().nextInt(max + 1) - min OR not.
Definitely not the same. You can sub in 2 numbers for max and min. You will see their differences.
Let your min be 7 and max be 9:
Random().nextInt((max - min) + 1) + min
// Random().nextInt((9 - 7) + 1) + 7
// Random().nextInt(3) + 7
// Randomly generates (0, 1, 2) + 7
// Randomly generates (7, 8, 9)
Now swap 7 and 9 into the other code snippet:
Random().nextInt(9 + 1) - 7
// Random().nextInt(10) - 7
// Randomly generates (0, 1, 2, 3, 4, 5, 6, 7, 8, 9) - 7
// Randomly generates (-7, -6, -5, -4, -3, -2, -1, 0, 1, 2)
One way for me to interpret how random.nextInt(val) works is by looking at the value of val. Let say if the final evaluation of val is 5. There are 5 possibilities to be randomly generated starting from 0. (i.e. 0,1,2,3,4)
