Create 15A Objects inside objects

Week 4: Writing classes/15A Objects inside objects

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+It is often useful to store an object inside other objects - 
+in effect, using your own class as the type of an attribute defined in another class:
+
+
+
+First, let's define the class Driver:
+class Driver {
+    private String name;
+    private int birthYear;
+    
+    public Driver(String name, int birthYear) {
+        this.name = name;
+        this.birthYear = birthYear;
+    }
+    
+    public String getName() {
+        return name;
+    }
+
+    public int getBirthYear() {
+        return birthYear;
+    }   
+}
+
+
+ 
+
+Next, the class Car is defined, with one attribute of type Driver:
+
+class Car {
+    private String brand;
+    private Driver driver;
+    
+    public Car(String brand, Driver driver) {
+        this.brand = brand;
+        this.driver = driver;
+    }
+
+    public String getBrand() {
+        return brand;
+    }
+
+    public Driver getDriver() {
+        return driver;
+    }  
+}
+
+
+ 
+If we have a Car object, and we want to know the name of the driver, 
+we can do that by first calling the method getDriver() and then calling the method getName() on the driver object:
+
+public class TestClass {
+    public static void main(String[] args) {
+        Driver d = new Driver("Vebastian Settel", 1987);
+        Car car = new Car("Maston Artin", d);
+        
+        System.out.println(car.getDriver().getName()); 
+    }
+}
+
+
+
+
+
+
+ 
+
+A class can also define a data structure to store objects from another class:
+
+Let us first define the class Book:
+
+class Book {
+    private String author;
+    private String name;
+    int pages;
+    
+    public Book(String author, String name, int pages) {
+        this.author = author;
+        this.name = name;
+        this.pages = pages;
+    }
+    
+    public String getAuthor() {
+        return author;
+    }
+    
+    public String getName() {
+        return name;
+    }
+    
+    public int getPages() {
+        return pages;
+    } 
+}
+ 
+
+Then you define the Bookcase class, where you can store books. 
+In practice, the bookcase stores the books in a list. 
+
+
+
+In the Bookcase class, you can conveniently add a method that 'returns all books by a single author in a new list':
+
+class Bookcase {
+    private ArrayList<Book> books;
+
+    // CONSTRUCTOR
+    public Bookcase() {
+        books = new ArrayList<>();
+    }
+    
+    public void addBook(Book book) {
+        books.add(book);
+    }
+    
+    public ArrayList<Book> authorsBooks(String authorName) {
+        ArrayList<Book> list  = new ArrayList<Book>();
+        for (Book b: books) {
+            if (b.getAuthor().equals(authorName)) {
+                list.add(b);
+            }
+        }
+        return list;
+    }
+}
+
+
+
+
+
+