started ex Z4

src/exercises/ex_n_bis/LibraryCatalog.java

@@ -0,0 +1,75 @@
+package exercises.ex_n_bis;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantReadWriteLock;
+
+public class LibraryCatalog {
+    private final Map<String, String> catalog = new HashMap<>();
+    private final ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
+    private final Lock readLock = lock.readLock();
+    private final Lock writeLock = lock.writeLock();
+
+    public LibraryCatalog() {
+
+    }
+
+    public ArrayList<Book> getBooks() {
+        ArrayList<Book> books = new ArrayList<>();
+        try {
+            readLock.lock();
+            catalog.forEach((title, author) -> {
+                books.add(new Book(title, author));
+            });
+        } finally {
+            readLock.unlock();
+        }
+        return books;
+    }
+
+    public String findBook(String title) {
+        String author;
+        try {
+            readLock.lock();
+            author = catalog.get(title);
+        } finally {
+            readLock.unlock();
+        }
+        if (author == null) {
+            System.out.println("The book '" + title + "' is not in the catalog");
+            return null;
+        }
+        return author;
+    }
+
+    public void addBook(String title, String author) {
+        try {
+            writeLock.lock();
+            catalog.put(title, author);
+        } finally {
+            writeLock.unlock();
+        }
+    }
+
+    public void removeBook(String title) {
+        try {
+            writeLock.lock();
+            catalog.remove(title);
+        } finally {
+            writeLock.unlock();
+        }
+    }
+
+    public void updateBook(String title, String newAuthor) {
+        try {
+            writeLock.lock();
+            catalog.replace(title, newAuthor);
+        } finally {
+            writeLock.unlock();
+        }
+    }
+
+    public record Book(String title, String author) {}
+}