How can I generate random number in specific range in Android?

Question

I want to generate random number in a specific range. (Ex. Range Between 65 to 80)

I try as per below code, but it is not very use full. It also returns the value greater then max. value(greater then 80).

Random r = new Random();
int i1 = (r.nextInt(80) + 65);

How can I generate random number between a range?

With [Kotlin](https://stackoverflow.com/a/45687695/8583692) you can do this: `val r = (0..10).random()` — Mahozad, Aug 26 '21 at 11:14

score 516 · Accepted Answer · edited Feb 14 '14 at 02:22

516

Random r = new Random();
int i1 = r.nextInt(80 - 65) + 65;

This gives a random integer between 65 (inclusive) and 80 (exclusive), one of 65,66,...,78,79.

edited Feb 14 '14 at 02:22

Mr. Polywhirl

answered May 17 '11 at 10:29

Ishtar

3

it won't work for negative numbers – Kirill Kulakov Jun 07 '13 at 21:21
7

If you need a negative number, use this and multiply by -1. You need a float, I think. – Allison Jan 04 '14 at 23:36
@Sirens: He could even generate two more numbers, then count differente between them (it can be negative or positive number ;)), and finaly multiply the original random number ;) – TomeeNS Sep 23 '15 at 21:48
2

simpler as possible: int myRandomInt = new Random().nextInt(80 - 65) + 65; – Alecs Jan 11 '16 at 11:14
8

I've been writing Java in one way or another for about 8 years and I still copy and paste this code whenever I need it, cheers – Saik Caskey Jun 19 '17 at 09:17
@TomeeNS that would weaken the randomness .. these arent actual random numbers, dont forget. – roberto tomás Aug 06 '17 at 14:05
can you help with this answer here: https://stackoverflow.com/q/46638945/6144372 I tried to use your code but failed. – Hammad Nasir Oct 09 '17 at 12:15
this is just pseudo-random! – larsaars Jun 09 '20 at 20:22

score 308 · Answer 2 · edited Dec 18 '15 at 23:10

308

int min = 65;
int max = 80;

Random r = new Random();
int i1 = r.nextInt(max - min + 1) + min;

Note that nextInt(int max) returns an int between 0 inclusive and max exclusive. Hence the +1.

edited Dec 18 '15 at 23:10

Saeid Yazdani

answered May 17 '11 at 10:29

Vivien Barousse

2 Answers2