Overview
This lecture explains getter and setter methods in Java, demonstrating how they protect and control access to object data using a Car class example.
Creating a Java Class and Attributes
- A
Car class is created with attributes: model (String), color (String), and price (int).
- A constructor initializes these attributes using parameters.
- Objects can be created from the
Car class and their attributes printed.
Access Modifiers and Data Protection
- By default, attributes are publicly accessible, allowing direct reading and modification.
- Changing an attribute, like
model, is easy if attributes are public, which may not be desired.
- Setting attributes as
private restricts access from outside the class.
Getter Methods (Read Access)
- Getter methods allow reading the values of private attributes.
- A getter method’s naming convention is
getAttributeName().
- Example:
public String getModel() { return this.model; }
- Getters can include additional logic, such as formatting or adding currency symbols.
Setter Methods (Write Access)
- Setter methods allow controlled modification of private attributes.
- Naming convention:
setAttributeName(), with a void return type.
- Example:
public void setColor(String color) { this.color = color; }
- Setters can include validation logic, e.g., price cannot be negative.
Controlling Readability and Writability
- If an attribute should not be modified after construction (e.g.,
model), do not provide a setter for it.
- Use the
final keyword to make an attribute immutable for extra security.
Example of Additional Logic in Setters
- In a setter for
price, check if the new value is negative. If so, output an error message and do not update the attribute.
Key Terms & Definitions
- Getter Method — A method that returns the value of a private attribute, making it readable.
- Setter Method — A method that changes the value of a private attribute, making it writable.
- Private Access Modifier — Keyword (
private) that restricts attribute access to within the class.
- Final Keyword — Keyword that prevents an attribute from being changed after initialization.
Action Items / Next Steps
- Practice creating getter and setter methods for a new class.
- Add validation logic to setters to enforce rules on attribute values.