Generating random integers in a specific range

Question!

I am trying to generate a random intvalue with Java, but in a specific range.

For example:

My range is 5-10, meaning that 5 is the smallest possible value and 10 is the biggest. Any other number in between these numbers is possible to be a value, too.

In Java, there is a method random() in the Math class, which returns a double value between 0.0 and 1.0. In the class Random there is the method nextInt(int n), which returns a random int value in the range of 0 (inclusive) and n (exclusive). I couldn't find a method, which returns a random integer value between two numbers.

I have tried the following things, but I still have problems: (minimum and maximum are the smallest and biggest numbers).

Solution 1:

randomNum = minimum + (int)(Math.random() * maximum); 

Problem:

randomNum can be bigger than maximum.

Solution 2:

Random rn = new Random();
int n = maximum - minimum + 1;
int i = rn.nextInt() % n;
randomNum =  minimum + i;

Problem:

randomNum can be smaller than minimum.

How do I solve these problems?

I have tried also browsing through the archive and found:

But I couldn't solve the problem.

By : user42155


Answers

This will generate Random numbers list with range (Min - Max) with no duplicate.

generateRandomListNoDuplicate(1000, 8000, 500);

Add this method.

private void generateRandomListNoDuplicate(int min, int max, int totalNoRequired) {
    Random rng = new Random();
    Set<Integer> generatedList = new LinkedHashSet<>();
    while (generatedList.size() < totalNoRequired) {
        Integer radnomInt = rng.nextInt(max - min + 1) + min;
        generatedList.add(radnomInt);
    }
}

Hope this will help you.



Generate a random number for the difference of min and max by using the nextint(n) method and then add min number to the result:

Random rn = new Random();
int result = rn.nextInt(max - min + 1) + min;
System.out.println(result);


You can do something like this:

import java.awt.*;
import java.io.*;
import java.util.*;
import java.math.*;

public class Test {

    public static void main(String[] args) {
        int first, second;

        Scanner myScanner = new Scanner(System.in);

        System.out.println("Enter first integer: ");
        int numOne;
        numOne = myScanner.nextInt();
        System.out.println("You have keyed in " + numOne);

        System.out.println("Enter second integer: ");
        int numTwo;
        numTwo = myScanner.nextInt();
        System.out.println("You have keyed in " + numTwo);

        Random generator = new Random();
        int num = (int)(Math.random()*numTwo);
        System.out.println("Random number: " + ((num>numOne)?num:numOne+num));
    }
}
By : thangaraj


This video can help you solving your question :)
By: admin