Java Random number between 100 and 500 which is a multiple of 10

Question

I want to generate random number between two numbers which are multiples of 10. For example, between 100 and 500, I want to generate a uniform distribution of 110, 120 ... 490, 500.

I think it is better to use Random.nextInt() as per THIS post. But not sure how to do that.

With a bit of arithmetic, `(Random.nextInt(40) + 10) * 10`gives you what you want, I think. — Ken Y-N, Sep 11 '17 at 05:12
Shouldn't it be `(Random.nextInt(40) + 11) * 10` because yours generates a distribution over 100, 110 ... 480, 490? — Florian Cramer, Sep 11 '17 at 05:18

score 1 · Answer 1 · answered Sep 11 '17 at 05:53

1

(Random.nextInt(41)+10)*10 is the correct answer. The Random.nextInt(41) will generate numbers between 0 to 40. The Random.nextInt(41)+10 will generate number from 0 to 50.

And Hence (Random.nextInt(41)+10)*10 will generate numbers between 100 and 500.Please note that 100 and 500 are also included in the result.

answered Sep 11 '17 at 05:53

Ashish Shukla

17
4

These are random numbers b/w 100 and 500. There will not be the guaranteed behavior of uniformity. – Ashish Shukla Sep 11 '17 at 06:07

score 1 · Accepted Answer · answered Sep 11 '17 at 06:03

1

You can use this function.

public int random()
{
     Random r=new Random();
     return (r.nextInt(41)+10)*10;
}

Read this Math.random() versus Random.nextInt(int)

Random.nextInt(n) is both more efficient and less biased than Math.random() * n

answered Sep 11 '17 at 06:03

SRIDHARAN

1,196
1
15
35

Do I need to instantiate Random every time ? – Andy897 Sep 11 '17 at 07:00
No not needed. In fact, re instantiate might increase duplicate rate! – SRIDHARAN Sep 11 '17 at 07:40
You have to declare it as static inside the class. (not inside the function) – SRIDHARAN Sep 11 '17 at 08:36

Java Random number between 100 and 500 which is a multiple of 10

2 Answers2