ComprehensiveSalaryAnalyzer.java

import java.text.NumberFormat;
import java.util.InputMismatchException;
import java.util.Locale;
import java.util.Scanner;

/**
 * Enhanced Salary Calculator
 * Calculates annual salary with comprehensive breakdown including
 * gross salary, allowances, deductions, and net pay
 * 
 * @author Muhammad Yamman Hammad
 * @version 2.0
 */
public class ComprehensiveSalaryAnalyzer {
    
    // Constants for calculations
    private static final int MONTHS_IN_YEAR = 12;
    private static final double DEFAULT_TAX_RATE = 0.15; // 15% tax rate
    private static final double INSURANCE_RATE = 0.05; // 5% insurance
    
    /**
     * Calculates and displays comprehensive annual salary breakdown
     * @param monthlySalary The base monthly salary
     * @param monthlyAllowance The monthly allowance amount
     * @param taxRate The tax rate to apply (as decimal, e.g., 0.15 for 15%)
     */
    public void calculateAnnualSalary(double monthlySalary, double monthlyAllowance, double taxRate) {
        // Input validation
        if (monthlySalary < 0 || monthlyAllowance < 0) {
            System.err.println("Error: Salary and allowance values cannot be negative!");
            return;
        }
        
        if (taxRate < 0 || taxRate > 1) {
            System.err.println("Error: Tax rate must be between 0 and 1 (0% to 100%)!");
            return;
        }
        
        // Calculations
        double annualBaseSalary = monthlySalary * MONTHS_IN_YEAR;
        double annualAllowances = monthlyAllowance * MONTHS_IN_YEAR;
        double grossAnnualSalary = annualBaseSalary + annualAllowances;
        
        // Calculate deductions
        double taxDeduction = grossAnnualSalary * taxRate;
        double insuranceDeduction = annualBaseSalary * INSURANCE_RATE;
        double totalDeductions = taxDeduction + insuranceDeduction;
        
        double netAnnualSalary = grossAnnualSalary - totalDeductions;
        
        // Format currency for display
        NumberFormat currencyFormat = NumberFormat.getCurrencyInstance(Locale.US);
        
        // Display comprehensive breakdown
        displaySalaryBreakdown(monthlySalary, monthlyAllowance, annualBaseSalary, 
                             annualAllowances, grossAnnualSalary, taxDeduction, 
                             insuranceDeduction, totalDeductions, netAnnualSalary, 
                             currencyFormat, taxRate);
    }
    
    /**
     * Displays a formatted salary breakdown
     */
    private void displaySalaryBreakdown(double monthlySalary, double monthlyAllowance,
                                      double annualBaseSalary, double annualAllowances,
                                      double grossAnnualSalary, double taxDeduction,
                                      double insuranceDeduction, double totalDeductions,
                                      double netAnnualSalary, NumberFormat currencyFormat,
                                      double taxRate) {
        
        System.out.println("\n" + "=".repeat(60));
        System.out.println("              ANNUAL SALARY BREAKDOWN");
        System.out.println("=".repeat(60));
        
        System.out.printf("Monthly Base Salary:        %s%n", currencyFormat.format(monthlySalary));
        System.out.printf("Monthly Allowances:         %s%n", currencyFormat.format(monthlyAllowance));
        System.out.println("-".repeat(40));
        
        System.out.printf("Annual Base Salary:         %s%n", currencyFormat.format(annualBaseSalary));
        System.out.printf("Annual Allowances:          %s%n", currencyFormat.format(annualAllowances));
        System.out.printf("Gross Annual Salary:        %s%n", currencyFormat.format(grossAnnualSalary));
        
        System.out.println("\nDEDUCTIONS:");
        System.out.printf("Tax (%.1f%%):                 %s%n", taxRate * 100, currencyFormat.format(taxDeduction));
        System.out.printf("Insurance (%.1f%%):           %s%n", INSURANCE_RATE * 100, currencyFormat.format(insuranceDeduction));
        System.out.printf("Total Deductions:           %s%n", currencyFormat.format(totalDeductions));
        
        System.out.println("-".repeat(40));
        System.out.printf("NET ANNUAL SALARY:          %s%n", currencyFormat.format(netAnnualSalary));
        System.out.printf("NET MONTHLY SALARY:         %s%n", currencyFormat.format(netAnnualSalary / MONTHS_IN_YEAR));
        System.out.println("=".repeat(60));
    }
    
    /**
     * Gets valid numeric input from user with error handling
     * @param scanner The Scanner object for input
     * @param prompt The prompt message to display
     * @param fieldName The name of the field being input (for error messages)
     * @return Valid double value
     */
    private double getValidInput(Scanner scanner, String prompt, String fieldName) {
        double value;
        while (true) {
            try {
                System.out.print(prompt);
                value = scanner.nextDouble();
                if (value < 0) {
                    System.out.println("Error: " + fieldName + " cannot be negative. Please enter a positive value.");
                    continue;
                }
                break;
            } catch (InputMismatchException e) {
                System.out.println("Error: Please enter a valid number for " + fieldName.toLowerCase() + ".");
                scanner.next(); // Clear invalid input
            }
        }
        return value;
    }
    
    /**
     * Gets valid tax rate input from user
     * @param scanner The Scanner object for input
     * @return Valid tax rate as decimal
     */
    private double getValidTaxRate(Scanner scanner) {
        double taxRate;
        while (true) {
            try {
                System.out.print("Enter tax rate percentage (0-100, default 15): ");
                String input = scanner.next().trim();
                
                if (input.isEmpty()) {
                    taxRate = DEFAULT_TAX_RATE;
                    break;
                }
                
                taxRate = Double.parseDouble(input) / 100.0; // Convert percentage to decimal
                
                if (taxRate < 0 || taxRate > 1) {
                    System.out.println("Error: Tax rate must be between 0 and 100 percent.");
                    continue;
                }
                break;
            } catch (NumberFormatException e) {
                System.out.println("Error: Please enter a valid tax rate percentage.");
            }
        }
        return taxRate;
    }
    
    /**
     * Main method - Entry point of the application
     */
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        ComprehensiveSalaryAnalyzer salaryCalculator = new ComprehensiveSalaryAnalyzer();
        
        try {
            System.out.println("=".repeat(60));
            System.out.println("         WELCOME TO ANNUAL SALARY CALCULATOR");
            System.out.println("=".repeat(60));
            
            // Get user inputs with validation
            double monthlySalary = salaryCalculator.getValidInput(input, 
                "Enter your monthly base salary: $", "Monthly salary");
            
            double monthlyAllowances = salaryCalculator.getValidInput(input, 
                "Enter your monthly allowances: $", "Monthly allowances");
            
            double taxRate = salaryCalculator.getValidTaxRate(input);
            
            // Calculate and display results
            salaryCalculator.calculateAnnualSalary(monthlySalary, monthlyAllowances, taxRate);
            
            // Ask if user wants to calculate again
            System.out.print("\nWould you like to calculate another salary? (y/n): ");
            String response = input.next().trim().toLowerCase();
            
            if (response.equals("y") || response.equals("yes")) {
                main(args); // Recursive call for another calculation
            } else {
                System.out.println("\nThank you for using the Annual Salary Calculator!");
            }
            
        } catch (Exception e) {
            System.err.println("An unexpected error occurred: " + e.getMessage());
        } finally {
            input.close();
        }
    }
}