Abstraction hides certain details of implementation and only displays necessary information to the consumer. Java achieves this by using abstract classes or interfaces.
Java abstract class:
- The
abstractkeyword is used to define an abstract class - An abstract class cannot be instantiated
- An abstract class can be inherited from another class ( which can be either abstract or not)
- An abstract class can have both abstract and regular methods (However, an abstract method cannot be defined in regular class)
Java abstract class example:
package com.devspeedup.javaabstract;
abstract class Vehicle {
int noOfWheels;
Vehicle(int noOfWheels) {
this.noOfWheels = noOfWheels;
}
public abstract void introduce();
public void drive() {
System.out.println("Drive on " + noOfWheels + " wheels");
}
}
class Car extends Vehicle {
Car(int noOfWheels) {
super(noOfWheels);
}
public void introduce() {
System.out.println("Hello! I am a car");
}
}
class Bike extends Vehicle {
Bike(int noOfWheels) {
super(noOfWheels);
}
public void introduce() {
System.out.println("Hello! I am a bike");
}
}
class Main {
public static void main (String[] args) {
Car car = new Car(4);
Bike bike = new Bike(2);
car.introduce();
car.drive();
bike.introduce();
bike.drive();
}
}
The result from running the main method in the Main class:
