Section 1: Notes

Basics of Classes

• A class is a blueprint for creating objects.
• A class defines attributes (fields/variables) and methods (functions) that describe the behavior of the objects created from the class.
• Example:

  public class Car {
      // Attributes
      String color;
      String model;
      int year;
      
      // Methods
      void drive() {
          System.out.println("The car is driving");
      }
  }

Visibility Levels

• public: Accessible from any other class.
• private: Accessible only within the same class.
• protected: Accessible within the same package and subclasses.
• default (no modifier): Accessible only within the same package.

    java
    Copy code
    public class Car {
        public String color;
        private String model;
        protected int year;
        int speed; // default
    }

Attributes

• Variables that hold the data associated with an object.
• Declared within a class but outside any method.

    java
    Copy code
    public class Car {
        String color; // attribute
        String model; // attribute
    }

Operations (Methods)

• Functions that define the behavior of objects.
• Can be used to perform operations, return values, or modify object state.

java
Copy code
public class Car {
    void drive() {
        System.out.println("The car is driving");
    }
}

Creating Objects and Accessing Variables

• Objects are instances of classes.

• Use the new keyword to create an object.

• Access attributes and methods using the dot . operator.

    java
    Copy code
    public class Car {
        String color;
        String model;
        
        void drive() {
            System.out.println("The car is driving");
        }
        
        public static void main(String[] args) {
            Car myCar = new Car(); 
            myCar.color = "Red";
            myCar.model = "Toyota";
            System.out.println(myCar.color); // Outputs: Red
            myCar.drive(); // Outputs: The car is driving
        }
    }
  

# Getters and Setters

- Methods that provide access to private attributes.
- Getters return the value of a private attribute.
- Setters allow modifying the value of a private attribute.
   

java
Copy code
public class Car {
    private String color;
    private String model;
    
    // Getter for color
    public String getColor() {
        return color;
    }
    
    // Setter for color
    public void setColor(String color) {
        this.color = color;
    }
    
    // Getter for model
    public String getModel() {
        return model;
    }
    
    // Setter for model
    public void setModel(String model) {
        this.model = model;
    }
}

`` `

Section 2: Basic Guided Questions

1. Creating a Class and Objects:

   • Write a class Dog with attributes name and breed.
   • Write a method bark() that prints "Woof!".
   • Create an object of the class and call the bark() method.

2. Using Visibility Levels:

   • Modify the Dog class to have name as public and breed as private.
   • Add a method getBreed() to return the breed.
   • Try accessing breed directly from another class and observe the result.
   • Explanation Required: Explain why breed cannot be accessed directly and how the getBreed() method allows access.
   • Create a class Person with the following attributes and methods:
     • private String name
     • protected int age
     • public String getName()
     • public void setName(String name)
     • protected void setAge(int age)
   • Try accessing the attributes and methods of the Person class from another class in the same package and from a different package.
   • Explanation Required: Explain the access levels for each visibility modifier when accessing the Person class attributes and methods.

3. Visibility Check for Classes and Methods in Packages:

   • Create a package mypackage and a class Person inside it.
   • Create another class TestPerson in the same package and try accessing the Person class.
   • Create another package anotherpackage and a class TestPersonInAnotherPackage inside it. Try accessing the Person class from this new class.
   • Explanation Required: Explain the class access levels within and across packages.

4. Using Getters and Setters:

   • Modify the Book class to make the attributes title and author private.
   • Add getters and setters for these attributes.
   • Try accessing the private attributes directly and explain the result.
   • Explanation Required: Explain the purpose of getters and setters and how they provide controlled access to private attributes.

Section 3: Comprehensive Question

Software Requirement Specification for a Library Management System:

The Library Management System (LMS) shall manage books and member details, including borrowing and returning books. The system shall consist of the following requirements:

1. Book Management:

   • The system shall allow adding new books with the following details: title, author, ISBN, and availability status.
   • The system shall allow searching for books by title.
   • The system shall allow updating the availability status of a book when it is borrowed or returned.

2. Member Management:

   • The system shall allow registering new members with their details: name and member ID.
   • The system shall allow searching for members by their member ID.
   • The system shall track books borrowed by each member.

3. Borrowing and Returning Books:

   • The system shall allow members to borrow available books.
   • The system shall update the book's availability status when borrowed.
   • The system shall allow members to return borrowed books.
   • The system shall update the book's availability status when returned.

4. Example Implementation:

Requirement: The system shall allow searching for books by title.

Implementation Steps:

• Store the list of books in an array.
• Loop through the array and compare each book's title with the search query.
• If a match is found, return the book details. Code Example:

java
Copy code
public class Library {
    private Book[] books;
    private int bookCount;

    public Library(int size) {
        books = new Book[size];
        bookCount = 0;
    }

    public void addBook(Book book) {
        if (bookCount < books.length) {
            books[bookCount] = book;
            bookCount++;
        }
    }

    public Book searchBookByTitle(String title) {
        for (int i = 0; i < bookCount; i++) {
            if (books[i].getTitle().equalsIgnoreCase(title)) {
                return books[i];
            }
        }
        return null;
    }
}