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 (min, max) 

(where min and max are ints), that returns something like this:

8 

(randomly)

If such a method does exist could you please link to the relevant documentation with your answer.

Thanks.

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UPDATE

Attempting to implement the full solution and I get the following error message:

class TestR { public static void main (String[]arg) { Random random = new Random() ; int randomNumber = random.nextInt(5) + 2; System.out.println (randomNumber) ; } } 

I'm still getting the same errors from the compiler:

TestR.java:5: cannot find symbol symbol : class Random location: class TestR Random random = new Random() ; ^ TestR.java:5: cannot find symbol symbol : class Random location: class TestR Random random = new Random() ; ^ TestR.java:6: operator + cannot be applied to Random.nextInt,int int randomNumber = random.nextInt(5) + 2; ^ TestR.java:6: incompatible types found : <nulltype> required: int int randomNumber = random.nextInt(5) + 2; ^ 4 errors 

What's going wrong here?

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

You can use Random.nextInt(n). This returns a random int in [0,n). Just using max-min+1 in place of n and adding min to the answer will give a value in the desired range.

Answer 3

public static int random_int(int Min, int Max) { return (int) (Math.random()*(Max-Min))+Min; } random_int(5, 9); // For example 

Answer 4

With Java 7 or above you could use

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

Javadoc: ThreadLocalRandom.nextInt

Answer 5

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 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)); 

Answer 7

This generates a random integer of size psize

public static Integer getRandom(Integer pSize) { if(pSize<=0) { return null; } Double min_d = Math.pow(10, pSize.doubleValue()-1D); Double max_d = (Math.pow(10, (pSize).doubleValue()))-1D; int min = min_d.intValue(); int max = max_d.intValue(); return RAND.nextInt(max-min) + min; } 

Answer 8

import java.util.Random;