Encapsulation Principle

Encapsulation is one of the 4 main OOP principles.

It protects the class data from access outside the class body.

Example of encapsulation

class Car { private // data inaccessible outside the class body: String model; int manifactureYear; public String getModel() { return this.model; } int getManifactureYear() { return this.manifactureYear; } void setModel(String modelValue) { this.model = modelValue; } void setManifactureYear(int manifactureYearValue) { this.manifactureYear = manifactureYearValue; } } public class Main { public static void main(String[] args) { Car car = new Car(); car.setModel("Toyota Corolla"); car.setManifactureYear(2020); // System.out.println("Model: " + car.model); System.out.println("Year: " + car.getManifactureYear()); System.out.println("Model: " + car.getModel()); } }

Result:

Year: 2020 Model: Toyota Corolla

Explanation:

• The private members can only be accessed / modified by functions defined inside the class (in this case getters and setters).
• If we uncomment line 36 the code won't compile. A direct access to private members cannot be done outside the class body.

Example of no encapsulation

class Car { public // data accessible outside the class body: String model; int manifactureYear; } public class Main { public static void main(String[] args) { Car car = new Car(); car.model = "Toyota Corolla"; car.manifactureYear = 2020; System.out.println("Year: " + car.manifactureYear); System.out.println("Model: " + car.model); } }

Output:

Year: 2020 Model: Toyota Corolla

All members are accessible outside the class body.