Overview
This lecture explains getter and setter methods in Java, demonstrating how they help control and protect access to object data through a Car class example.
Creating the Car Class
- A Car class is defined with attributes: model (String), color (String), and price (int).
- A constructor initializes these attributes with parameters.
Public vs. Private Attributes
- Public attributes can be accessed and modified directly from outside the class.
- To prevent unwanted changes, use the
private access modifier for attributes.
Getter Methods
- Getter methods provide controlled access to private fields (read-only).
- Naming convention:
getAttributeName() returns the field value.
- Additional logic (like formatting) can be added within getters.
Setter Methods
- Setter methods allow controlled modification of private fields (write access).
- Naming convention:
setAttributeName(value) assigns a new value to the field.
- Not all attributes need setters (e.g., model should not change once set).
Making Attributes Read-Only or Write-Only
- Omit the setter to make an attribute read-only.
- Add the
final keyword to prevent even setter modifications.
Adding Validation Logic
- Setters can include checks (e.g., price must not be negative).
- If validation fails, show an error and skip updating the value.
Example Usage
- Getter methods are used to retrieve values:
car.getColor(), car.getModel(), car.getPrice().
- Setter methods update values when allowed:
car.setColor("blue"), car.setPrice(5000).
Key Terms & Definitions
- Getter Method — A function that returns the value of a private attribute (makes it readable).
- Setter Method — A function that sets the value of a private attribute (makes it writable).
- Private Attribute — A variable only accessible within its own class.
- Final Keyword — Prevents a variable from being modified after initialization.
- Validation — Logic in setters to ensure only acceptable data is set.
Action Items / Next Steps
- Practice creating a Java class with private attributes, getters, and setters.
- Experiment adding validation logic in setter methods.
- Review Java concepts of access modifiers and encapsulation.