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Introduction to Java

Random Number Generator within range - Java Program

import java.util.Scanner;
import java.util.Random;
 
public class RandomInRange {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        Random rand = new Random();
 
        System.out.println("===== RANDOM NUMBER GENERATOR =====");
 
        System.out.print("Enter minimum value: ");
        int min = sc.nextInt();
 
        System.out.print("Enter maximum value: ");
        int max = sc.nextInt();
 
        if (min > max) {
            System.out.println("Invalid range! Minimum cannot be greater than maximum.");
            return;
        }
 
        // Generate random number in range [min, max]
        int randomNum = rand.nextInt((max - min) + 1) + min;
 
        System.out.println("\nRandom Number between " + min + " and " + max + " is: " + randomNum);
    }
}
 

 
OUTPUT :
===== RANDOM NUMBER GENERATOR =====
Enter minimum value: 10
Enter maximum value: 50

Random Number between 10 and 50 is: 34

Explanation of the Program

✅ Import Random and Scanner

import java.util.Random;

import java.util.Scanner;

• Scanner → read min & max from user
• Random → generate random numbers

✅ Take Range Input

int min = sc.nextInt();

int max = sc.nextInt();

The user enters:

• Minimum value
• Maximum value

✅ Validate Range

if (min > max) {

    System.out.println("Invalid range!");

    return;

}

Prevents invalid input like min = 50, max = 10.

✅ Random Number Formula

int randomNum = rand.nextInt((max - min) + 1) + min;

✅ Explanation:

• rand.nextInt(n) → generates a number from 0 to n-1
• So for a custom range [min, max], use:

rand.nextInt(max−min+1)+min\text{rand.nextInt}(max - min + 1) + minrand.nextInt(max−min+1)+min

Example:
min = 10, max = 50 → nextInt(41) gives 0–40 → add 10 → final range 10–50

✅ Display Result

System.out.println("Random Number between " + min + " and " + max + " is: " + randomNum);