Generating a Random Number between 1 and 10 Java [duplicate]

Question

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?

Answer 1

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 

Answer 2

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.