Overview
This lecture explains getter and setter methods in Java, demonstrating how they protect object data and control access or modification of class attributes.
Creating a Car Class
- Define a
Car class with attributes: model (String), color (String), and price (int).
- Use a constructor to initialize
model, color, and price when creating a Car object.
- Car attributes are public by default, allowing direct access and modification.
Using Private Attributes
- Make class attributes private (
private String model, etc.) to restrict direct access from outside the class.
- Directly accessing private attributes from outside the class results in access errors.
Getter Methods
- Getter methods allow reading private attributes using a public method (e.g.,
getModel()).
- Getters typically follow the naming convention
getAttributeName.
- Getter methods return the current value of a private attribute.
- Additional logic, such as formatting, can be added to getter methods (e.g., returning price with a currency symbol).
Setter Methods
- Setter methods allow modifying private attributes using a public method (e.g.,
setColor(String color)).
- Setters follow the naming convention
setAttributeName.
- Only include setter methods for attributes you want to allow changes (e.g.,
color and price, but not model).
- Add logic to setter methods to validate changes, such as preventing negative prices.
Controlling Attribute Accessibility
- Attributes without setter methods are read-only from outside the class.
- Adding the
final keyword to an attribute makes it immutable after initialization.
- Setters can be omitted to prevent unwanted changes to sensitive data.
Key Terms & Definitions
- Getter Method — A public method to retrieve (read) the value of a private class attribute.
- Setter Method — A public method to update (write) the value of a private class attribute.
- Private Attribute — A class variable declared with
private, restricting direct external access.
- final Keyword — Prevents a variable from being reassigned after it is set.
- Constructor — Special method to initialize objects when they are created.
Action Items / Next Steps
- Practice creating a Java class with private attributes, getters, and setters.
- Add logic to setter methods for attribute validation.
- Experiment with omitting setters for read-only attributes and using
final for immutability.