#26 - java, javascript, php y typescript

Author: eulogioep

Roadmap/26 - SOLID SRP/java/eulogioep.java

@@ -0,0 +1,387 @@
+// Archivo: eulogioep.java
+
+/**
+ * PRINCIPIO DE RESPONSABILIDAD ÚNICA (SRP)
+ * 
+ * El Principio de Responsabilidad Única establece que:
+ * "Una clase debe tener una única razón para cambiar"
+ * 
+ * Este principio nos ayuda a:
+ * - Crear código más mantenible
+ * - Facilitar las pruebas unitarias
+ * - Reducir el acoplamiento
+ * - Mejorar la cohesión del código
+ * - Facilitar la reutilización
+ */
+
+ import java.util.ArrayList;
+ import java.util.Date;
+ import java.util.List;
+ import java.util.UUID;
+ import java.util.stream.Collectors;
+ 
+ public class eulogioep {
+     public static void main(String[] args) {
+         // Ejemplo de uso del sistema
+         try {
+             // Creación de los managers
+             BookManager bookManager = new BookManager();
+             UserManager userManager = new UserManager();
+             LoanManager loanManager = new LoanManager(bookManager, userManager);
+ 
+             // Agregar un libro
+             Book book = bookManager.addBook("El Quijote", "Miguel de Cervantes", 5);
+             System.out.println("Libro agregado: " + book);
+ 
+             // Registrar un usuario
+             User user = userManager.registerUser("Juan Pérez", "USER001", "juan@email.com");
+             System.out.println("Usuario registrado: " + user);
+ 
+             // Realizar un préstamo
+             Loan loan = loanManager.loanBook(user.getId(), book.getId());
+             System.out.println("Préstamo realizado: " + loan);
+ 
+             // Devolver el libro
+             loanManager.returnBook(user.getId(), book.getId());
+             System.out.println("Libro devuelto exitosamente");
+ 
+             // Verificar el estado del libro
+             Book updatedBook = bookManager.findBook(book.getId());
+             System.out.println("Estado actual del libro: " + updatedBook);
+ 
+         } catch (Exception e) {
+             System.err.println("Error: " + e.getMessage());
+         }
+     }
+ }
+ 
+ // ========== IMPLEMENTACIÓN INCORRECTA (Violando SRP) ==========
+ 
+ /**
+  * Esta implementación viola el SRP porque la clase Library maneja múltiples responsabilidades:
+  * 1. Gestión de libros
+  * 2. Gestión de usuarios
+  * 3. Gestión de préstamos
+  */
+ class Library {
+     private List<Book> books;
+     private List<User> users;
+     private List<Loan> loans;
+ 
+     public Library() {
+         this.books = new ArrayList<>();
+         this.users = new ArrayList<>();
+         this.loans = new ArrayList<>();
+     }
+ 
+     // Gestión de libros
+     public void addBook(String title, String author, int copies) {
+         Book book = new Book(title, author, copies);
+         books.add(book);
+     }
+ 
+     public void removeBook(String bookId) {
+         books.removeIf(book -> book.getId().equals(bookId));
+     }
+ 
+     // Gestión de usuarios
+     public void registerUser(String name, String id, String email) {
+         User user = new User(name, id, email);
+         users.add(user);
+     }
+ 
+     public void removeUser(String userId) {
+         users.removeIf(user -> user.getId().equals(userId));
+     }
+ 
+     // Gestión de préstamos
+     public void loanBook(String userId, String bookId) throws Exception {
+         Book book = books.stream()
+                         .filter(b -> b.getId().equals(bookId))
+                         .findFirst()
+                         .orElseThrow(() -> new Exception("Libro no encontrado"));
+ 
+         User user = users.stream()
+                         .filter(u -> u.getId().equals(userId))
+                         .findFirst()
+                         .orElseThrow(() -> new Exception("Usuario no encontrado"));
+ 
+         if (book.getAvailableCopies() <= 0) {
+             throw new Exception("No hay copias disponibles");
+         }
+ 
+         book.decrementCopies();
+         loans.add(new Loan(userId, bookId, new Date()));
+     }
+ 
+     public void returnBook(String userId, String bookId) throws Exception {
+         Loan loan = findLoan(userId, bookId);
+         if (loan == null) {
+             throw new Exception("Préstamo no encontrado");
+         }
+ 
+         Book book = books.stream()
+                         .filter(b -> b.getId().equals(bookId))
+                         .findFirst()
+                         .orElse(null);
+ 
+         if (book != null) {
+             book.incrementCopies();
+         }
+ 
+         loans.removeIf(l -> l.getUserId().equals(userId) && l.getBookId().equals(bookId));
+     }
+ 
+     private Loan findLoan(String userId, String bookId) {
+         return loans.stream()
+                    .filter(l -> l.getUserId().equals(userId) && l.getBookId().equals(bookId))
+                    .findFirst()
+                    .orElse(null);
+     }
+ }
+ 
+ // ========== IMPLEMENTACIÓN CORRECTA (Siguiendo SRP) ==========
+ 
+ /**
+  * BookManager: Responsable únicamente de la gestión de libros
+  */
+ class BookManager {
+     private List<Book> books;
+ 
+     public BookManager() {
+         this.books = new ArrayList<>();
+     }
+ 
+     public Book addBook(String title, String author, int copies) {
+         Book book = new Book(title, author, copies);
+         books.add(book);
+         return book;
+     }
+ 
+     public void removeBook(String bookId) {
+         books.removeIf(book -> book.getId().equals(bookId));
+     }
+ 
+     public Book findBook(String bookId) {
+         return books.stream()
+                    .filter(book -> book.getId().equals(bookId))
+                    .findFirst()
+                    .orElse(null);
+     }
+ 
+     public void updateBookCopies(String bookId, int change) {
+         Book book = findBook(bookId);
+         if (book != null) {
+             if (change > 0) {
+                 book.incrementCopies();
+             } else {
+                 book.decrementCopies();
+             }
+         }
+     }
+ 
+     public List<Book> getAllBooks() {
+         return new ArrayList<>(books);
+     }
+ }
+ 
+ /**
+  * UserManager: Responsable únicamente de la gestión de usuarios
+  */
+ class UserManager {
+     private List<User> users;
+ 
+     public UserManager() {
+         this.users = new ArrayList<>();
+     }
+ 
+     public User registerUser(String name, String id, String email) {
+         User user = new User(name, id, email);
+         users.add(user);
+         return user;
+     }
+ 
+     public void removeUser(String userId) {
+         users.removeIf(user -> user.getId().equals(userId));
+     }
+ 
+     public User findUser(String userId) {
+         return users.stream()
+                    .filter(user -> user.getId().equals(userId))
+                    .findFirst()
+                    .orElse(null);
+     }
+ 
+     public List<User> getAllUsers() {
+         return new ArrayList<>(users);
+     }
+ }
+ 
+ /**
+  * LoanManager: Responsable únicamente de la gestión de préstamos
+  */
+ class LoanManager {
+     private List<Loan> loans;
+     private final BookManager bookManager;
+     private final UserManager userManager;
+ 
+     public LoanManager(BookManager bookManager, UserManager userManager) {
+         this.loans = new ArrayList<>();
+         this.bookManager = bookManager;
+         this.userManager = userManager;
+     }
+ 
+     public Loan loanBook(String userId, String bookId) throws Exception {
+         Book book = bookManager.findBook(bookId);
+         User user = userManager.findUser(userId);
+ 
+         if (book == null || user == null) {
+             throw new Exception("Libro o usuario no encontrado");
+         }
+ 
+         if (book.getAvailableCopies() <= 0) {
+             throw new Exception("No hay copias disponibles");
+         }
+ 
+         bookManager.updateBookCopies(bookId, -1);
+         Loan loan = new Loan(userId, bookId, new Date());
+         loans.add(loan);
+         return loan;
+     }
+ 
+     public void returnBook(String userId, String bookId) throws Exception {
+         Loan loan = findLoan(userId, bookId);
+         if (loan == null) {
+             throw new Exception("Préstamo no encontrado");
+         }
+ 
+         bookManager.updateBookCopies(bookId, 1);
+         loans.removeIf(l -> l.getUserId().equals(userId) && l.getBookId().equals(bookId));
+     }
+ 
+     private Loan findLoan(String userId, String bookId) {
+         return loans.stream()
+                    .filter(loan -> loan.getUserId().equals(userId) && loan.getBookId().equals(bookId))
+                    .findFirst()
+                    .orElse(null);
+     }
+ 
+     public List<Loan> getAllLoans() {
+         return new ArrayList<>(loans);
+     }
+ }
+ 
+ // Clases de modelo
+ class Book {
+     private final String id;
+     private final String title;
+     private final String author;
+     private int availableCopies;
+ 
+     public Book(String title, String author, int availableCopies) {
+         this.id = UUID.randomUUID().toString();
+         this.title = title;
+         this.author = author;
+         this.availableCopies = availableCopies;
+     }
+ 
+     public String getId() {
+         return id;
+     }
+ 
+     public String getTitle() {
+         return title;
+     }
+ 
+     public String getAuthor() {
+         return author;
+     }
+ 
+     public int getAvailableCopies() {
+         return availableCopies;
+     }
+ 
+     public void incrementCopies() {
+         this.availableCopies++;
+     }
+ 
+     public void decrementCopies() {
+         this.availableCopies--;
+     }
+ 
+     @Override
+     public String toString() {
+         return "Book{" +
+                "id='" + id + '\'' +
+                ", title='" + title + '\'' +
+                ", author='" + author + '\'' +
+                ", availableCopies=" + availableCopies +
+                '}';
+     }
+ }
+ 
+ class User {
+     private final String id;
+     private final String name;
+     private final String email;
+ 
+     public User(String name, String id, String email) {
+         this.name = name;
+         this.id = id;
+         this.email = email;
+     }
+ 
+     public String getId() {
+         return id;
+     }
+ 
+     public String getName() {
+         return name;
+     }
+ 
+     public String getEmail() {
+         return email;
+     }
+ 
+     @Override
+     public String toString() {
+         return "User{" +
+                "id='" + id + '\'' +
+                ", name='" + name + '\'' +
+                ", email='" + email + '\'' +
+                '}';
+     }
+ }
+ 
+ class Loan {
+     private final String userId;
+     private final String bookId;
+     private final Date loanDate;
+ 
+     public Loan(String userId, String bookId, Date loanDate) {
+         this.userId = userId;
+         this.bookId = bookId;
+         this.loanDate = loanDate;
+     }
+ 
+     public String getUserId() {
+         return userId;
+     }
+ 
+     public String getBookId() {
+         return bookId;
+     }
+ 
+     public Date getLoanDate() {
+         return loanDate;
+     }
+ 
+     @Override
+     public String toString() {
+         return "Loan{" +
+                "userId='" + userId + '\'' +
+                ", bookId='" + bookId + '\'' +
+                ", loanDate=" + loanDate +
+                '}';
+     }
+ }