how to generate positive and negative numbers in Java

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How to generate random positive and negative numbers in java

Hello I am trying to create a method in Java to create negative and positive values in Java.

the problem is that I don't know how to get this programmed but I do know the logic.. here is what I tought it should be

 Random generator = new Random();

 for (int i = 0; i < 21; i++)
 {
       System.out.print(generator.nextInt(100) + 1);
       System.out.println();
 }

but with the code above I get only positive values and I need values between -100 and 100 but how can I accomplish something like that?

Pablo Santa Cruz · Accepted Answer · 2012-10-19T11:41:21.477

16

You can use:

Random generator = new Random();
int val = 100 - generator.nextInt(201);

Or, as JoachimSauer suggested in the comments:

int val = generator.nextInt(201) - 100;

edited Oct 19 '12 at 11:41

answered Oct 19 '12 at 11:32

Pablo Santa Cruz

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Personally I'd use `generator.nextInt(200) - 100`, but that's just a matter of taste. – Joachim Sauer Oct 19 '12 at 11:34
Ah thanks alot that was the trick :) didn't know i could substract it like that! – Reshad Oct 19 '12 at 11:35
@JoachimSauer: sure. I think that's better. Will update the answer. Thanks! – Pablo Santa Cruz Oct 19 '12 at 11:35
1

@PabloSantaCruz by the way, you'd better denote the type of generator (i.e. Random) somewhere in your answer. I noticed that it's not written neither in the question nor in the answer =) – Juvanis Oct 19 '12 at 11:38

score 10 · Answer 2 · answered Oct 19 '12 at 11:38

10

The general formula is

int val = rand.nextInt(max - min + 1) + min;

Note that min and max can be negative. (max > min)

answered Oct 19 '12 at 11:38

Peter Lawrey

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how to generate positive and negative numbers in Java

2 Answers2