Introduction

In this tutorial, we will learn how to create a simple employee database system using Java, which supports CRUD (Create, Read, Update, and Delete) operations. This will allow users to manage employee records effectively in a database.

Objective

The main objective of this project is to develop a Java application that allows you to perform the following CRUD operations on an employee database:

• Create new employee records.
• Read and display existing employee records.
• Update existing employee records.
• Delete employee records from the database.

Code Implementation

import java.util.*;

class Employee {
    int id;
    String name;
    String position;
    double salary;

    Employee(int id, String name, String position, double salary) {
        this.id = id;
        this.name = name;
        this.position = position;
        this.salary = salary;
    }
}

public class EmployeeDatabase {
    private static Map<Integer, Employee> employeeDB = new HashMap<>();
    private static Scanner scanner = new Scanner(System.in);

    public static void main(String[] args) {
        while (true) {
            System.out.println("\nEmployee Database - CRUD Operations");
            System.out.println("1. Add Employee");
            System.out.println("2. View Employees");
            System.out.println("3. Update Employee");
            System.out.println("4. Delete Employee");
            System.out.println("5. Exit");
            System.out.print("Choose an option: ");
            int choice = scanner.nextInt();
            scanner.nextLine();  // Clear buffer

            switch (choice) {
                case 1:
                    addEmployee();
                    break;
                case 2:
                    viewEmployees();
                    break;
                case 3:
                    updateEmployee();
                    break;
                case 4:
                    deleteEmployee();
                    break;
                case 5:
                    System.out.println("Exiting...");
                    System.exit(0);
                default:
                    System.out.println("Invalid option. Please try again.");
            }
        }
    }

    // Add a new employee
    public static void addEmployee() {
        System.out.print("Enter Employee ID: ");
        int id = scanner.nextInt();
        scanner.nextLine();  // Clear buffer
        System.out.print("Enter Employee Name: ");
        String name = scanner.nextLine();
        System.out.print("Enter Employee Position: ");
        String position = scanner.nextLine();
        System.out.print("Enter Employee Salary: ");
        double salary = scanner.nextDouble();

        Employee employee = new Employee(id, name, position, salary);
        employeeDB.put(id, employee);
        System.out.println("Employee added successfully!");
    }

    // View all employees
    public static void viewEmployees() {
        if (employeeDB.isEmpty()) {
            System.out.println("No employees found.");
        } else {
            System.out.println("\nEmployee List:");
            for (Employee emp : employeeDB.values()) {
                System.out.println("ID: " + emp.id + ", Name: " + emp.name + ", Position: " + emp.position + ", Salary: " + emp.salary);
            }
        }
    }

    // Update an employee record
    public static void updateEmployee() {
        System.out.print("Enter Employee ID to update: ");
        int id = scanner.nextInt();
        scanner.nextLine();  // Clear buffer

        if (employeeDB.containsKey(id)) {
            Employee emp = employeeDB.get(id);
            System.out.println("Current Info - Name: " + emp.name + ", Position: " + emp.position + ", Salary: " + emp.salary);

            System.out.print("Enter new Name: ");
            emp.name = scanner.nextLine();
            System.out.print("Enter new Position: ");
            emp.position = scanner.nextLine();
            System.out.print("Enter new Salary: ");
            emp.salary = scanner.nextDouble();

            System.out.println("Employee record updated successfully!");
        } else {
            System.out.println("Employee with ID " + id + " not found.");
        }
    }

    // Delete an employee record
    public static void deleteEmployee() {
        System.out.print("Enter Employee ID to delete: ");
        int id = scanner.nextInt();

        if (employeeDB.containsKey(id)) {
            employeeDB.remove(id);
            System.out.println("Employee deleted successfully!");
        } else {
            System.out.println("Employee with ID " + id + " not found.");
        }
    }
}

Program Explanation

This Java program allows the user to manage employee data using the following CRUD operations:

• Add Employee: The user is prompted to enter the employee’s ID, name, position, and salary. The employee record is then added to a map (HashMap).
• View Employees: The user can view a list of all employees currently in the database. If no records exist, the program informs the user accordingly.
• Update Employee: The user can update an employee’s name, position, or salary by providing the employee’s ID.
• Delete Employee: The user can delete an employee by entering the employee’s ID.

How to Run the Program

Follow these steps to run the program:

1. Ensure you have Java installed on your system. If not, download and install it from the official Oracle website.
2. Copy the code into a file named EmployeeDatabase.java.
3. Open a terminal (command prompt) and navigate to the directory containing the file.
4. Compile the program using the command javac EmployeeDatabase.java.
5. Run the program using the command java EmployeeDatabase.