Overview
This lecture explains getter and setter methods in Java, demonstrating how they protect object data and control access and modification of class attributes using a Car class example.
Creating a Car Class
- Define a Car class with attributes: String model, String color, and int price.
- Use a constructor to initialize model, color, and price attributes.
- Create a Car object by providing specific values for model, color, and price.
Attribute Access and Encapsulation
- By default, class attributes are publicly accessible and can be changed directly.
- Use the
private keyword to restrict direct access to class attributes.
- Private attributes cannot be accessed or modified directly from outside the class.
Getter Methods
- Getter methods allow reading of private attributes.
- Convention: method name starts with
get followed by the attribute name (e.g., getModel).
- Example:
public String getModel() { return this.model; }
- Getter methods can include additional logic, such as formatting or validation.
Setter Methods
- Setter methods allow controlled modification of private attributes.
- Convention: method name starts with
set followed by the attribute name (e.g., setColor).
- Example:
public void setColor(String color) { this.color = color; }
- Setter methods can include logic to validate new values (e.g., reject negative prices).
Readable vs Writable Attributes
- Some attributes (like model) should be readable but not writable; omit the setter method to prevent changes.
- Use the
final keyword if an attribute should not be modified after initialization.
Example of Enhanced Setter Logic
- Include checks in setter methods to prevent invalid values (e.g., disallow negative prices in setPrice).
Key Terms & Definitions
- Getter Method — A method that returns the value of a private attribute (makes a field readable).
- Setter Method — A method that updates the value of a private attribute (makes a field writable).
- Private Attribute — A class variable declared with the
private keyword, hidden from outside the class.
- Encapsulation — The practice of restricting access to internal object data using methods.
- Final — A keyword used to make an attribute unchangeable after initialization.
Action Items / Next Steps
- Practice creating classes with private attributes and implement getter and setter methods.
- Add validation logic to setter methods for data integrity.
- Review Java documentation on encapsulation, getters, and setters.