How to Generate a Random Number in Java

Submitted by donbermoy on Tuesday, May 27, 2014 - 16:24.

In this tutorial, we will going to create a program that generates a random number using Java. We will just use the Math.random() function which returns a random number between 0.0 and 1.0 Now let's start this tutorial! 1. Open JCreator or NetBeans and make a java program with a file name of randomNumber.java. 2. Import javax.swing package. Hence we will use the JOptionPane.showMessageDialog than the System.out.print.

import javax.swing.*;

3. Initialize your variable in your Main, i have here variable number as an integer that will be equal to the Math.random() function. Take note: Math.random() returns a random number between 0.0 and 1.0, including 0.0 but not including 1.0 which means this function covers to be in double or decimal data type in nature. I also put the JOptionPane.showMessageDialog for displaying and generating the random number output.

        double number = Math.random();
      
         JOptionPane.showMessageDialog(null, "Generated number: " + number);

Now, we will create again a random number by multiplying Math.random() result with a number will give a range of random number between, for instance 0.0 to 50 as shown in my code below.

        number = Math.random() * 50;
        JOptionPane.showMessageDialog(null, "Generated number: " + number);

The example below creates random number between 100.0 and 300.0.

        number = 200 + (Math.random() * 100);
        JOptionPane.showMessageDialog(null, "Generated number: " + number);

Now, we will create an integer random number from 100 to 200.

 int random =  100 + (int)(Math.random() * 100);
        JOptionPane.showMessageDialog(null, "Generated number: " + random);

Output: output

Full source code:

import javax.swing.*;
public class randomNumber
{
    public static void main(String[] args)
    {
 
        double number = Math.random();
         JOptionPane.showMessageDialog(null, "Generated number: " + number);
         
 
        number = Math.random() * 50;
        JOptionPane.showMessageDialog(null, "Generated number: " + number);
        
 
        number = 200 + (Math.random() * 100);
        JOptionPane.showMessageDialog(null, "Generated number: " + number);
        
        int random =  100 + (int)(Math.random() * 100);
        JOptionPane.showMessageDialog(null, "Generated number: " + random);
    }
}

Best Regards, Engr. Lyndon Bermoy IT Instructor/System Developer/Android Developer/Freelance Programmer If you have some queries, feel free to contact the number or e-mail below. Mobile: 09488225971 Landline: 826-9296 E-mail:[email protected] Add and Follow me on Facebook: https://www.facebook.com/donzzsky Visit and like my page on Facebook at: https://www.facebook.com/BermzISware

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