I want to generate a number between 1 and 10 in Java.

Here is what I tried:

Random rn = new Random(); int answer = rn.nextInt(10) + 1;

Is there a way to tell what to put in the parenthesis () when calling the nextInt method and what to add?

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3 Answers

As the documentation says, this method call returns "a pseudorandom, uniformly distributed int value between 0 (inclusive) and the specified value (exclusive)". This means that you will get numbers from 0 to 9 in your case. So you've done everything correctly by adding one to that number.

Generally speaking, if you need to generate numbers from min to max (including both), you write

random.nextInt(max - min + 1) + min
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The standard way to do this is as follows:

Provide:

  • min Minimum value
  • max Maximum value

and get in return a Integer between min and max, inclusive.

Random rand = new Random(); // nextInt as provided by Random is exclusive of the top value so you need to add 1 int randomNum = rand.nextInt((max - min) + 1) + min;

See the relevant JavaDoc.

As explained by Aurund, Random objects created within a short time of each other will tend to produce similar output, so it would be a good idea to keep the created Random object as a field, rather than in a method.

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This will work for generating a number 1 - 10. Make sure you import Random at the top of your code.

import java.util.Random;

If you want to test it out try something like this.

Random rn = new Random(); for(int i =0; i < 100; i++) { int answer = rn.nextInt(10) + 1; System.out.println(answer); }

Also if you change the number in parenthesis it will create a random number from 0 to that number -1 (unless you add one of course like you have then it will be from 1 to the number you've entered).

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