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Java Program - Number Checker

Concept Explanation

What is it?

This program uses a multi-way if-else-if ladder to classify a number based on its relationship to zero.

Why is it important?

Conditional logic is the foundation of decision-making in programming. This is one of the simplest examples of how code can branch.

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Algorithm

1. Start
2. Accept a number from the user.
3. If number > 0, display "Positive".
4. Else If number < 0, display "Negative".
5. Else, display "Zero".
6. End

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Implementations

Java (JDK 17)

import java.util.Scanner;

public class NumberChecker {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        System.out.print("Enter a number: ");
        int num = sc.nextInt();

        if (num > 0) {
            System.out.println(num + " is POSITIVE.");
        } else if (num < 0) {
            System.out.println(num + " is NEGATIVE.");
        } else {
            System.out.println("The number is ZERO.");
        }

        sc.close();
    }
}

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Complexity Analysis

• Time Complexity: O(1)
• Space Complexity: O(1)

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Flowchart

graph TD
    A[Start] --> B[Input num]
    B --> C{num > 0?}
    C -- Yes --> D[Positive]
    C -- No --> E{num < 0?}
    E -- Yes --> F[Negative]
    E -- No --> G[Zero]
    D --> H[End]
    F --> H
    G --> H

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Interview Tips

• Be ready to explain the difference between if and if-else if. (In an ladder, only the first true condition executes).

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"Programming is about making decisions based on conditions." - Anonymous