Largest Of Three Numbers In Java Using If Else

Finding the largest among three numbers is a fundamental programming task, crucial for understanding conditional logic and basic comparisons. In this article, you will learn how to determine the largest number using different if-else statement approaches in Java.

Problem Statement

The core problem involves comparing three numerical values and identifying which one holds the highest value. This comparison needs to account for all possible scenarios where any of the three numbers could be the largest, or if multiple numbers are equal.

Example

Let's consider three numbers: num1 = 10, num2 = 25, and num3 = 15. The expected output for this set of numbers would be 25, as it is the largest among the three.

Background & Knowledge Prerequisites

To understand the solutions presented, readers should have a basic understanding of:

• Java Variables: How to declare and initialize integer or floating-point variables.
• Input/Output (I/O): How to take input from the user using Scanner.
• Comparison Operators: Operators like >, <, >=, <=, ==.
• if-else Statements: Basic syntax and flow of conditional logic.
• Logical Operators: Specifically, the && (logical AND) operator.

Use Cases or Case Studies

Identifying the largest of a small set of numbers is a common building block in various applications:

• Data Validation: Ensuring an input value falls within a specific range compared to other limits.
• Simple Sorting Algorithms: As a sub-task in sorting three elements, though not a general-purpose sort.
• Game Development: Determining the highest score, the strongest player, or the best stat among a few options.
• Financial Applications: Finding the highest transaction amount, highest interest rate, or best performing asset in a small comparison.
• Temperature Monitoring: Identifying the peak temperature reading from three sensors over a period.

Solution Approaches

We will explore two common methods using if-else statements to find the largest of three numbers.

Approach 1: Using Nested if-else Statements

This approach uses a hierarchical structure of if-else conditions to compare the numbers sequentially.

• One-line summary: Compares the first number with the second, then the larger of those with the third, to find the ultimate largest.

// Largest of Three Numbers using Nested If-Else
import java.util.Scanner;

// Main class containing the entry point of the program
public class Main {
    public static void main(String[] args) {
        // Step 1: Declare variables to store the three numbers
        int num1, num2, num3;

        // Step 2: Create a Scanner object to get user input
        Scanner scanner = new Scanner(System.in);

        // Step 3: Prompt the user to enter the three numbers
        System.out.print("Enter the first number: ");
        num1 = scanner.nextInt();

        System.out.print("Enter the second number: ");
        num2 = scanner.nextInt();

        System.out.print("Enter the third number: ");
        num3 = scanner.nextInt();

        // Step 4: Determine the largest number using nested if-else statements
        int largest;

        if (num1 >= num2) {
            if (num1 >= num3) {
                largest = num1; // num1 is largest
            } else {
                largest = num3; // num3 is largest
            }
        } else { // num2 > num1
            if (num2 >= num3) {
                largest = num2; // num2 is largest
            } else {
                largest = num3; // num3 is largest
            }
        }

        // Step 5: Print the largest number
        System.out.println("The largest number is: " + largest);

        // Step 6: Close the scanner to prevent resource leak
        scanner.close();
    }
}

Run

• Sample output

  Enter the first number: 10
  Enter the second number: 25
  Enter the third number: 15
  The largest number is: 25

• Stepwise explanation

1. The program declares three integer variables (num1, num2, num3) to store the input.
2. A Scanner object is initialized to read input from the console.
3. The user is prompted to enter three numbers, which are then stored in the respective variables.
4. The main if condition checks if num1 is greater than or equal to num2.

• If num1 >= num2 is true, it means num1 is a candidate for the largest. Inside this block, another if condition checks if num1 is also greater than or equal to num3.
• If num1 >= num3 is true, then num1 is the largest.
• Otherwise (num1 < num3), num3 must be the largest (because num1 was already greater than or equal to num2, but num3 is greater than num1).
• If num1 >= num2 is false (meaning num2 is strictly greater than num1), then num2 is a candidate for the largest. Inside this else block, another if condition checks if num2 is greater than or equal to num3.
• If num2 >= num3 is true, then num2 is the largest.
• Otherwise (num2 < num3), num3 must be the largest (because num2 was already greater than num1, but num3 is greater than num2).

1. Finally, the program prints the value stored in the largest variable.
2. The Scanner resource is closed.

Approach 2: Using Logical AND (&&) Operator

This approach uses logical AND to combine multiple comparison conditions in a single if-else if-else chain, making the code more flat and sometimes easier to read.

• One-line summary: Each condition directly checks if a number is greater than or equal to both other numbers simultaneously.

// Largest of Three Numbers using Logical AND
import java.util.Scanner;

// Main class containing the entry point of the program
public class Main {
    public static void main(String[] args) {
        // Step 1: Declare variables to store the three numbers
        int num1, num2, num3;

        // Step 2: Create a Scanner object to get user input
        Scanner scanner = new Scanner(System.in);

        // Step 3: Prompt the user to enter the three numbers
        System.out.print("Enter the first number: ");
        num1 = scanner.nextInt();

        System.out.print("Enter the second number: ");
        num2 = scanner.nextInt();

        System.out.print("Enter the third number: ");
        num3 = scanner.nextInt();

        // Step 4: Determine the largest number using if-else if-else with logical AND
        if (num1 >= num2 && num1 >= num3) {
            System.out.println("The largest number is: " + num1);
        } else if (num2 >= num1 && num2 >= num3) {
            System.out.println("The largest number is: " + num2);
        } else {
            // If neither num1 nor num2 is the largest, num3 must be
            System.out.println("The largest number is: " + num3);
        }

        // Step 5: Close the scanner to prevent resource leak
        scanner.close();
    }
}

Run

• Sample output

  Enter the first number: 10
  Enter the second number: 25
  Enter the third number: 15
  The largest number is: 25

• Stepwise explanation

1. Similar to the previous approach, variables are declared, and a Scanner is used to get three integer inputs from the user.
2. The first if condition checks if num1 is greater than or equal to both num2 AND num3.

• If num1 >= num2 && num1 >= num3 is true, num1 is the largest, and it is printed.

1. If the first if condition is false, the else if condition is evaluated. It checks if num2 is greater than or equal to both num1 AND num3.

• If num2 >= num1 && num2 >= num3 is true, num2 is the largest, and it is printed.

1. If both the if and else if conditions are false, it implicitly means that num3 must be the largest among the three (since num1 and num2 were not the largest), so the else block executes, printing num3.
2. The Scanner resource is closed.

Conclusion

Determining the largest of three numbers using if-else statements is a foundational exercise in programming conditional logic. Both nested if-else and if-else if-else with logical AND operators provide effective solutions. While nested if-else clarifies sequential comparisons, the logical AND approach often results in flatter, more concise code for this specific problem.

Summary

• Problem: Identify the highest value among three given numbers.
• Nested if-else: Compares numbers in a hierarchical manner, suitable for understanding layered conditions.
• Logical AND (&&): Combines multiple conditions efficiently, leading to a more direct comparison approach.
• Readability: Both methods are clear; the logical AND method often provides a more streamlined code for multiple simultaneous comparisons.
• Practicality: These methods are fundamental for basic comparisons and decision-making in various programming scenarios.