Objects

Key value pairs

We use a class to create an object. Objects allow us to store values against keys in a structured way.

public class Main {
  public static void main(String[] args) {
    Book book = new Book("The Handmaid's Tale", 1985, true);
  }
}

Accessing public properties

We can access public properties stored in the object using a . dot.

public class Main {
  public static void main(String[] args) {
    Book book = new Book("The Handmaid's Tale", 1985, true);

    System.out.println(book.title); // The Handmaid's Tale
    System.out.println(book.year); // 1985
    System.out.println(book.isAvailable); // true
  }
}

Updating public properties

We can update public properties by directly assigning to them.

public class Main {
  public static void main(String[] args) {
    Book book = new Book("The Handmaid's Tale", 1985, true);

    System.out.println(book.isAvailable); // true
    book.isAvailable = false;
    System.out.println(book.isAvailable); // false
  }
}

Adding new properties

We cannot directly add new properties to a created object.

public class Main {
  public static void main(String[] args) {
    Book book = new Book("The Handmaid's Tale", 1985, true);

    book.author = "Margaret Atwood" // error
  }
}