How do I generate a random integer between min and max in Java?

Question

What method returns a random int between a min and max? Or does no such method exist?

What I\'m looking for is something like this:

NAMEOFMETHOD (mi         


        

Answer 1

Construct a Random object at application startup:

Random random = new Random();

Then use Random.nextInt(int):

int randomNumber = random.nextInt(max + 1 - min) + min;

Note that the both lower and upper limits are inclusive.

Answer 2

With Java 7 or above you could use

ThreadLocalRandom.current().nextInt(int origin, int bound)

Javadoc: ThreadLocalRandom.nextInt

Answer 3

import java.util.Random;

Answer 4

As the solutions above do not consider the possible overflow of doing max-min when min is negative, here another solution (similar to the one of kerouac)

public static int getRandom(int min, int max) {
    if (min > max) {
        throw new IllegalArgumentException("Min " + min + " greater than max " + max);
    }      
    return (int) ( (long) min + Math.random() * ((long)max - min + 1));
}

this works even if you call it with:

getRandom(Integer.MIN_VALUE, Integer.MAX_VALUE) 

Answer 5

public static int random_int(int Min, int Max)
{
     return (int) (Math.random()*(Max-Min))+Min;
}

random_int(5, 9); // For example

Answer 6

Using the Random class is the way to go as suggested in the accepted answer, but here is a less straight-forward correct way of doing it if you didn't want to create a new Random object :

min + (int) (Math.random() * (max - min + 1));