Conditional Constructs in Java

Chapter 8

Conditional Constructs in Java

Class 10 - Logix Kips ICSE Computer Applications with BlueJ

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Java Program: Menu Driven Program - Composite Number & Smallest Digit

41. Using the switch statement, write a menu driven program:

To check and display whether a number input by the user is a composite number or not.
A number is said to be composite, if it has one or more than one factors excluding 1 and the number itself.
Example: 4, 6, 8, 9...
To find the smallest digit of an integer that is input:
Sample input: 6524
Sample output: Smallest digit is 2
For an incorrect choice, an appropriate error message should be displayed.

📋 Menu Options

Check whether a number is Composite
Find the Smallest Digit of a number

Java

import java.util.Scanner;
 
public class MenuCompositeSmallestDigit {
    public static void main(String[] args) {
 
        // Title
        System.out.println("MENU DRIVEN PROGRAM");
        System.out.println("-------------------");
        System.out.println("1. Check Composite Number");
        System.out.println("2. Find Smallest Digit");
 
        Scanner sc = new Scanner(System.in);
 
        System.out.print("Enter your choice: ");
        int choice = sc.nextInt();
 
        switch (choice) {
 
            case 1:
                System.out.print("Enter a number: ");
                int num = sc.nextInt();
                int count = 0;
 
                for (int i = 2; i <= num / 2; i++) {
                    if (num % i == 0)
                        count++;
                }
 
                if (count > 0)
                    System.out.println(num + " is a Composite Number");
                else
                    System.out.println(num + " is NOT a Composite Number");
                break;
 
            case 2:
                System.out.print("Enter an integer: ");
                int n = sc.nextInt();
                int smallest = 9;
 
                while (n > 0) {
                    int digit = n % 10;
                    if (digit < smallest)
                        smallest = digit;
                    n = n / 10;
                }
 
                System.out.println("Smallest digit is " + smallest);
                break;
 
            default:
                System.out.println("Invalid choice! Please select 1 or 2.");
        }
 
        sc.close();
    }
}

Output

Sample Run 1 

Enter your choice: 1
Enter a number: 6
6 is a Composite Number

Sample Run 2 

Enter your choice: 2
Enter an integer: 6524
Smallest digit is 2

Invalid Choice

Enter your choice: 5
Invalid choice! Please select 1 or 2.

📝 Explanation

🔹 Composite Number Check

Counts factors excluding 1 and the number
If factor count > 0 → Composite

🔹 Smallest Digit

Extracts digits using % 10
Compares each digit to find the smallest

🔹 switch-case

Executes logic based on user choice
Displays error message for invalid input