How would I generate random numbers ranging from -9 to 9?

Question

        double random1 = Math.random() * 9 + -9;
        double random2 = Math.random() * -9 + 9;

I need randomly generated numbers ranging from -9 to 9 using Math.random. When I use this code I have here it only prints the first number as a negative number.I've ran this multiple times and still the first number is always negative while the second is positive. How can I fix this to be more random? Thanks

determine the length of result space (from `-9` to `9`), multiply the random value by this length, subtract the lower bound of the result space. — Turing85, Apr 07 '18 at 19:14
While asking questions you should get list of potentially related questions. One of them should be [How do I generate random integers within a specific range in Java?](https://stackoverflow.com/q/363681) (taken from list called `Related` at right side of this page). Did you visit it? — Pshemo, Apr 07 '18 at 19:15

score 2 · Answer 1 · answered Apr 07 '18 at 19:14

2

Math.random() generates a number between 0 and 1.

How about multiplying by 18 and then subtracting 9?

answered Apr 07 '18 at 19:14

camickr

321,443
19
166
288

score 1 · Answer 2 · answered May 07 '19 at 02:50

From jdk-7 you can use ThreadLocalRandom

public int nextInt(int origin, int bound)

Returns a pseudorandom int value between the specified origin (inclusive) and the specified bound (exclusive).

ThreadLocalRandom.current().nextInt(-9, 10) // will generate from -9>=x<10

score 0 · Answer 3 · answered Apr 07 '18 at 19:18

0

When you want a value between a number min and a number max :

Math.random() * ((max - min) + 1) + min

answered Apr 07 '18 at 19:18

Sébastien S.

1,444
8
14

How would I generate random numbers ranging from -9 to 9?

3 Answers3