Java
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1// Base class for different types of library users
2class Member {
3    private String name;
4
5    public Member(String name) {
6        this.name = name;
7    }
8
9    public void checkOutBook(Book book) {
10        System.out.println(name + " checked out " + book.getBookType() + " book " + book.getTitle() + ".");
11    }
12}
13
14// Base class for different types of books
15abstract class Book {
16    private String title;
17
18    public Book(String title) {
19        this.title = title;
20    }
21
22    public String getTitle() {
23        return title;
24    }
25
26    public abstract String getBookType();
27}
28
29// Inherits from Book, represents a digital book
30class DigitalBook extends Book {
31    public DigitalBook(String title) {
32        super(title);
33    }
34
35    @Override
36    public String getBookType() {
37        return "Digital";
38    }
39}
40
41// Inherits from Book, represents a physical book
42class PhysicalBook extends Book {
43    public PhysicalBook(String title) {
44        super(title);
45    }
46
47    @Override
48    public String getBookType() {
49        return "Physical";
50    }
51}
52
53// Library class that manages members and books
54class Library {
55    private ArrayList<Member> members;
56    private ArrayList<Book> books;
57
58    public Library() {
59        members = new ArrayList<Member>();
60        books = new ArrayList<Book>();
61    }
62
63    public void addMember(Member member) {
64        members.add(member);
65    }
66
67    public void addBook(Book book) {
68        books.add(book);
69    }
70}
71
72public class Main {
73    public static void main(String[] args) {
74        Library myLibrary = new Library();
75
76        Member alice = new Member("Alice");
77        Member bob = new Member("Bob");
78
79        myLibrary.addMember(alice);
80        myLibrary.addMember(bob);
81
82        Book digitalBook = new DigitalBook("The Java Handbook");
83        Book physicalBook = new PhysicalBook("Learning Java Design Patterns");
84
85        myLibrary.addBook(digitalBook);
86        myLibrary.addBook(physicalBook);
87
88        alice.checkOutBook(digitalBook);  // Prints: Alice checked out Digital book The Java Handbook.
89        bob.checkOutBook(physicalBook);   // Prints: Bob checked out Physical book Learning Java Design Patterns.
90    }
91}

Java
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1// Define the basic Shape class
2abstract class Shape {
3    // Abstract method that will be implemented in each subclass
4    public abstract void draw();
5}
6
7// Define the Circle class
8class Circle extends Shape {
9    // Implement the draw method for circle
10    @Override
11    public void draw() {
12        System.out.println("Drawing a circle.");
13    }
14}
15
16// Define the Square class
17class Square extends Shape {
18    // Implement the draw method for square
19    @Override
20    public void draw() {
21        System.out.println("Drawing a square.");
22    }
23}
24
25// Define the ShapeComposite class
26class ShapeComposite extends Shape {
27    // Initialize with an empty list of shapes
28    private ArrayList<Shape> shapes;
29
30    public ShapeComposite() {
31        shapes = new ArrayList<Shape>();
32    }
33
34    // Add a new shape to the composite
35    public void addShape(Shape shape) {
36        shapes.add(shape);
37    }
38
39    // Implement the draw method to draw each shape in composite
40    @Override
41    public void draw() {
42        for (Shape shape : shapes) {
43            shape.draw();
44        }
45    }
46}
47
48public class Main {
49    public static void main(String[] args) {
50        Circle circle = new Circle();
51        Square square = new Square();
52
53        // Drawing individual shapes
54        circle.draw();  // Output: Drawing a circle.
55        square.draw();  // Output: Drawing a square.
56
57        // Create a ShapeComposite instance for composite shapes
58        ShapeComposite compositeShape = new ShapeComposite();
59
60        // Add individual shapes to the composite
61        compositeShape.addShape(circle);
62        compositeShape.addShape(square);
63
64        // Drawing the composite shape
65        compositeShape.draw();
66        // Output:
67        // Drawing a circle.
68        // Drawing a square.
69    }
70}