Overview
This lecture explains getter and setter methods in Java, showing how they control and protect access to object data in a class.
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.
- Attributes are initially public, allowing direct access and modification.
Using Private Access Modifier
- Add the
private keyword to attributes to restrict direct access from outside the class.
- Private attributes cannot be directly read or modified from outside the class.
Getter Methods
- Getter methods allow reading private fields from outside the class.
- Naming convention:
getAttributeName(), e.g., getModel().
- Return the value of the corresponding private attribute.
- Getters can include additional logic, such as formatting or validation.
Setter Methods
- Setter methods allow writing (updating) private fields from outside the class.
- Naming convention:
setAttributeName(newValue), e.g., setColor(String color).
- Assign the new value to the corresponding attribute.
- Setters can include validation logic, like preventing a negative price.
Controlling Access with Getters and Setters
- Only implement setters for attributes you want to allow modification (e.g., color and price, but not model).
- Do not create a setter for read-only attributes to keep them immutable.
- Use the
final keyword for attributes that should never change (stronger immutability).
Example of Validation in Setters
- Within a setter, check for invalid input (e.g., price < 0) and prevent changes if validation fails.
- Output an error message if invalid data is provided; otherwise, update the attribute.
Key Terms & Definitions
- Getter Method — A method that returns the value of a private attribute (read access).
- Setter Method — A method that sets or updates the value of a private attribute (write access).
- Private Attribute — An attribute declared with the
private keyword, restricting access to within the class.
- Constructor — A special method called to initialize an object when it is created.
- Final Keyword — Prevents an attribute from being modified after its initial assignment.
Action Items / Next Steps
- Practice writing getter and setter methods in a new Java class.
- Experiment with applying validation logic in setter methods.
- Try making some attributes
final and observe how it affects mutability.