Introduction to Classes and Objects

Study Notes

Class: A blueprint or template for creating objects with shared properties and behaviors. It defines a set of attributes (fields/variables) and methods to represent the object's state and actions.
Object: An instance of a class, representing a real-world entity with a state and behavior. Objects have unique values for their attributes and can perform actions defined by the class methods.
Example:
- Class: Student
  - Attributes: id (integer), name (String)
  - Methods: None shown in the example
- Object: s1 (an instance of the Student class). s1.id and s1.name would hold specific values representing a particular student.

Constructor: Special method within a class that automatically initializes objects of that class when they are created using the new keyword.
- Constructors have the same name as the class.
- They do not have a return type, not even void.
Purpose: Sets initial values for the object's attributes, ensuring a consistent and meaningful starting state.

Default Constructor: Provided by Java if no constructors are defined. It initializes attributes with default values (0 for numeric types, null for reference types).
Parameterized Constructor: Takes parameters to initialize object attributes with specific values during creation. It allows for more flexible object creation based on the provided data.
Copy Constructor: Creates a new object by copying the state of an existing object of the same class. It's useful for creating new objects with the same initial values as a template object.

Method: A collection of statements that perform a specific task.
- Methods are used to encapsulate code for better organization and reusability.
- They can operate on data associated with the object (instance methods) or perform general tasks (static methods).
Method Overloading: The ability to have multiple methods within a class that share the same name but have different parameters (e.g., different data types, number of arguments).
- Method overloading allows you to create methods that handle similar operations but work with different input types or scenarios. Java uses the parameter list to distinguish overloaded methods.