Conditional Constructs in Java

Chapter 9

Conditional Constructs in Java

Class 9 - Logix Kips ICSE Computer Applications with BlueJ

Share with a Friend

Java Programs - Composite Number & Smallest Digit (Menu-Driven)

Using the switch statement, write a menu driven program:

1. 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...

2. 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.

Java

import java.util.Scanner;
 
public class MenuDrivenNumberCheck {
    public static void main(String[] args) {
 
        Scanner sc = new Scanner(System.in);
 
        System.out.println("----- MENU -----");
        System.out.println("1. Check Composite Number");
        System.out.println("2. Find Smallest Digit");
 
        System.out.print("Enter your choice (1 or 2): ");
        int choice = sc.nextInt();
 
        switch (choice) {
 
            case 1: // Composite Number Check
                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++;
                        break;
                    }
                }
 
                if (count > 0) {
                    System.out.println(num + " is a Composite Number.");
                } else {
                    System.out.println(num + " is NOT a Composite Number.");
                }
                break;
 
            case 2: // Smallest Digit
                System.out.print("Enter an integer: ");
                int n = sc.nextInt();
 
                int smallest = 9;
                int digit;
 
                while (n > 0) {
                    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

Output 1 : (Composite Number)
SAMPLE INPUT : 
Enter your choice (1 or 2): 1
Enter a number: 9

SAMPLE OUTPUT : 
9 is a Composite Number.

Output 2 : (Not Composite)
SAMPLE INPUT : 
Enter your choice (1 or 2): 1
Enter a number: 7

SAMPLE OUTPUT : 
7 is NOT a Composite Number.

Output 3 : (Smallest Digit)
SAMPLE INPUT : 
Enter your choice (1 or 2): 2
Enter an integer: 6524

SAMPLE OUTPUT : 
Smallest digit is 2

Output 4 : (Invalid Choice)
SAMPLE INPUT : 
Enter your choice (1 or 2): 5

SAMPLE OUTPUT : 
Invalid choice! Please select 1 or 2.

Explanation

1. Menu using switch

The program allows the user to choose between two operations.
switch executes the selected case.

2. Composite Number Logic

A number is composite if it has a factor other than 1 and itself.
Loop checks divisibility from 2 to num/2.

3. Smallest Digit Logic

Digits are extracted using % 10.
Minimum digit is tracked using a variable.

4. Default Case

Displays an error message for invalid menu choices.