diff --git a/lesson_09/oop/oop_app/src/main/java/com/codedifferently/lesson9/richhawkins/AlreadyCheckedOutException.java b/lesson_09/oop/oop_app/src/main/java/com/codedifferently/lesson9/richhawkins/AlreadyCheckedOutException.java
new file mode 100644
index 00000000..3bfec5a4
--- /dev/null
+++ b/lesson_09/oop/oop_app/src/main/java/com/codedifferently/lesson9/richhawkins/AlreadyCheckedOutException.java
@@ -0,0 +1,7 @@
+package main.java.com.codedifferently.lesson9.richhawkins;
+
+public class AlreadyCheckedOutException extends RuntimeException {
+  public AlreadyCheckedOutException(String message) {
+    super(message);
+  }
+}
diff --git a/lesson_09/oop/oop_app/src/main/java/com/codedifferently/lesson9/richhawkins/Book.java b/lesson_09/oop/oop_app/src/main/java/com/codedifferently/lesson9/richhawkins/Book.java
new file mode 100644
index 00000000..debf63f2
--- /dev/null
+++ b/lesson_09/oop/oop_app/src/main/java/com/codedifferently/lesson9/richhawkins/Book.java
@@ -0,0 +1,60 @@
+package main.java.com.codedifferently.lesson9.richhawkins;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class Book {
+  private String title;
+  private int isbn;
+  private List<String> authors = new ArrayList<>();
+  private int numberOfPages;
+  private boolean checkedOut;
+
+  public String getTitle() {
+    return title;
+  }
+
+  public void setTitle(String title) {
+    this.title = title;
+  }
+
+  public int getIsbn() {
+    return isbn;
+  }
+
+  public void setIsbn(int isbn) {
+    this.isbn = isbn;
+  }
+
+  public List<String> getAuthors() {
+    return authors;
+  }
+
+  public void setAuthors(List<String> authors) {
+    this.authors = authors;
+  }
+
+  public int getNumberOfPages() {
+    return numberOfPages;
+  }
+
+  public void setNumberOfPages(int numberOfPages) {
+    this.numberOfPages = numberOfPages;
+  }
+
+  public boolean getCheckedOut() {
+    return checkedOut;
+  }
+
+  public void setCheckedOut(boolean checkedOut) {
+    this.checkedOut = checkedOut;
+  }
+
+  public Book(String title, int isbn, List<String> authors, int numberOfPages, boolean checkedOut) {
+    this.title = title;
+    this.isbn = isbn;
+    this.authors = authors;
+    this.numberOfPages = numberOfPages;
+    this.checkedOut = checkedOut;
+  }
+}
diff --git a/lesson_09/oop/oop_app/src/main/java/com/codedifferently/lesson9/richhawkins/DuplicatePatronException.java b/lesson_09/oop/oop_app/src/main/java/com/codedifferently/lesson9/richhawkins/DuplicatePatronException.java
new file mode 100644
index 00000000..17b179a1
--- /dev/null
+++ b/lesson_09/oop/oop_app/src/main/java/com/codedifferently/lesson9/richhawkins/DuplicatePatronException.java
@@ -0,0 +1,7 @@
+package main.java.com.codedifferently.lesson9.richhawkins;
+
+public class DuplicatePatronException extends RuntimeException {
+  public DuplicatePatronException(String message) {
+    super(message);
+  }
+}
diff --git a/lesson_09/oop/oop_app/src/main/java/com/codedifferently/lesson9/richhawkins/Library.java b/lesson_09/oop/oop_app/src/main/java/com/codedifferently/lesson9/richhawkins/Library.java
new file mode 100644
index 00000000..221b13f1
--- /dev/null
+++ b/lesson_09/oop/oop_app/src/main/java/com/codedifferently/lesson9/richhawkins/Library.java
@@ -0,0 +1,54 @@
+package main.java.com.codedifferently.lesson9.richhawkins;
+
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.List;
+
+public class Library {
+  private HashSet<Book> bookCollection = new HashSet<>();
+  private List<Patron> patrons = new ArrayList<>();
+
+  public HashSet<Book> getBookCollection() {
+    return bookCollection;
+  }
+
+  public List<Patron> getPatrons() {
+    return patrons;
+  }
+
+  public void addBook(Book book) {
+    bookCollection.add(book);
+  }
+
+  public void removeBook(Book book) {
+    bookCollection.remove(book);
+  }
+
+  public void registerNewPatron(Patron patron) {
+    if (patrons.contains(patron)) {
+      throw new DuplicatePatronException("Error: This patron already exists.");
+    }
+    patrons.add(patron);
+  }
+
+  public void checkOutBook(Book book, Patron patron, Library library) {
+    if (book.getCheckedOut()) {
+      throw new AlreadyCheckedOutException("Error: The book is already checked out.");
+    }
+
+    if (patrons.contains(patron) && library.getBookCollection().contains(book)) {
+      book.setCheckedOut(true);
+      patron.getCheckedOutBooks().add(book.getTitle());
+    } else {
+      throw new IllegalArgumentException(
+          "Error: Either the patron is not registered or the book is not in the library's collection.");
+    }
+  }
+
+  public void checkBookIn(Book book, Patron patron, Library library) {
+    if (book.getCheckedOut() && patrons.contains(patron) && library.bookCollection.contains(book)) {
+      book.setCheckedOut(false);
+      patron.getCheckedOutBooks().remove(book.getTitle());
+    }
+  }
+}
diff --git a/lesson_09/oop/oop_app/src/main/java/com/codedifferently/lesson9/richhawkins/Patron.java b/lesson_09/oop/oop_app/src/main/java/com/codedifferently/lesson9/richhawkins/Patron.java
new file mode 100644
index 00000000..f8b23202
--- /dev/null
+++ b/lesson_09/oop/oop_app/src/main/java/com/codedifferently/lesson9/richhawkins/Patron.java
@@ -0,0 +1,28 @@
+package main.java.com.codedifferently.lesson9.richhawkins;
+
+import java.util.HashSet;
+
+public class Patron {
+  private String name;
+  private HashSet<String> checkedOutBooks = new HashSet<>();
+
+  public String getName() {
+    return name;
+  }
+
+  public void setName(String name) {
+    this.name = name;
+  }
+
+  public HashSet<String> getCheckedOutBooks() {
+    return checkedOutBooks;
+  }
+
+  public void setCheckedOutBooks(HashSet<String> checkedOutBooks) {
+    this.checkedOutBooks = checkedOutBooks;
+  }
+
+  public Patron(String name) {
+    this.name = name;
+  }
+}
diff --git a/lesson_09/oop/oop_app/src/test/java/com/codedifferently/lesson9/richhawkins/LibraryProjectTest.java b/lesson_09/oop/oop_app/src/test/java/com/codedifferently/lesson9/richhawkins/LibraryProjectTest.java
new file mode 100644
index 00000000..73cda863
--- /dev/null
+++ b/lesson_09/oop/oop_app/src/test/java/com/codedifferently/lesson9/richhawkins/LibraryProjectTest.java
@@ -0,0 +1,148 @@
+package test.java.com.codedifferently.lesson9.richhawkins;
+
+import static org.junit.jupiter.api.Assertions.*;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.List;
+import main.java.com.codedifferently.lesson9.richhawkins.AlreadyCheckedOutException;
+import main.java.com.codedifferently.lesson9.richhawkins.Book;
+import main.java.com.codedifferently.lesson9.richhawkins.Library;
+import main.java.com.codedifferently.lesson9.richhawkins.Patron;
+import org.junit.jupiter.api.Test;
+
+public class LibraryProjectTest {
+  @Test
+  public void testBookAccessors() {
+    List<String> authors = new ArrayList<>();
+    authors.add("John Doe");
+    authors.add("Jane Doe");
+
+    Book book = new Book("A Story About Something", 7654321, authors, 350, false);
+    List<String> newAuthors = new ArrayList<>();
+    newAuthors.add("Abe Lincoln");
+
+    book.setCheckedOut(true);
+    assertEquals(true, book.getCheckedOut());
+    book.setTitle("Fun");
+    assertEquals("Fun", book.getTitle());
+    book.setIsbn(1234567);
+    assertEquals(1234567, book.getIsbn());
+    book.setAuthors(newAuthors);
+    assertEquals(newAuthors, book.getAuthors());
+    book.setNumberOfPages(250);
+    assertEquals(250, book.getNumberOfPages());
+  }
+
+  @Test
+  public void testPatronAccessors() {
+    Patron patron = new Patron("Rich");
+    HashSet<String> books = new HashSet<>();
+    books.add("A New Tale");
+    books.add("A Newer Tale");
+
+    patron.setName("Nick");
+    assertEquals("Nick", patron.getName());
+    patron.setCheckedOutBooks(books);
+    assertEquals(books, patron.getCheckedOutBooks());
+  }
+
+  @Test
+  public void testAddBook() {
+    Library library = new Library();
+    List<String> authors = new ArrayList<>();
+    authors.add("John Doe");
+    Book book = new Book("Test Book", 1234, authors, 145, false);
+
+    library.addBook(book);
+
+    assertTrue(library.getBookCollection().contains(book));
+  }
+
+  @Test
+  public void testRemoveBook() {
+    Library library = new Library();
+    List<String> authors = new ArrayList<>();
+    authors.add("John Doe");
+    Book book = new Book("Test Book", 1234, authors, 145, false);
+
+    library.removeBook(book);
+
+    assertTrue(!library.getBookCollection().contains(book));
+  }
+
+  @Test
+  public void testRegisterNewPatron() {
+    Library library = new Library();
+    Patron patron = new Patron("Rich");
+
+    library.registerNewPatron(patron);
+
+    assertTrue(library.getPatrons().contains(patron));
+  }
+
+  @Test
+  public void testCheckOutBook() {
+    // Create a library, book, and patrons
+    Library library = new Library();
+    Book book = new Book("Test Book", 1234, new ArrayList<>(), 145, false);
+    Patron patron1 = new Patron("John Doe");
+    Patron patron2 = new Patron("Jane Doe");
+
+    // Add the book to the library
+    library.addBook(book);
+
+    // Register patron1 with the library
+    library.registerNewPatron(patron1);
+
+    // Check out the book to patron1
+    library.checkOutBook(book, patron1, library);
+
+    // Verify that the book is checked out
+    assertTrue(book.getCheckedOut());
+
+    // Verify that patron1 has the book checked out
+    assertTrue(patron1.getCheckedOutBooks().contains(book.getTitle()));
+
+    // Try to check out the book to patron2 (should fail)
+    try {
+      library.checkOutBook(book, patron2, library);
+      fail("Expected AlreadyCheckedOutException was not thrown");
+    } catch (AlreadyCheckedOutException e) {
+      // Expected exception, do nothing
+    }
+    // Verify that the book is still checked out by patron1
+    assertTrue(book.getCheckedOut());
+    assertTrue(patron1.getCheckedOutBooks().contains(book.getTitle()));
+  }
+
+  @Test
+  public void testCheckBookIn() {
+    // Create a library, book, and patron
+    Library library = new Library();
+    Book book = new Book("Test Book", 1234, new ArrayList<>(), 145, false);
+    Patron patron = new Patron("John Doe");
+
+    // Add the book to the library
+    library.addBook(book);
+
+    // Register the patron with the library
+    library.registerNewPatron(patron);
+
+    // Check out the book to the patron
+    library.checkOutBook(book, patron, library);
+
+    // Verify that the book is checked out
+    assertTrue(book.getCheckedOut());
+
+    // Check the book back in
+    library.checkBookIn(book, patron, library);
+
+    // Verify that the book is no longer checked out
+    assertFalse(book.getCheckedOut());
+
+    // Verify that the patron no longer has the book checked out
+    assertFalse(patron.getCheckedOutBooks().contains(book.getTitle()));
+  }
+}