Java Inheritance

By Connor Young

Definition:

Inheritance: Refers to classes that can be derived from other classes, thereby inheriting fields and methods from those classes. This includes the use of subclasses and superclasses.
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  • The classes Car and Truck are subclasses of the class Vehicle
  • The class Vehicle is the superclass of the classes Car and Truck
  • These classes are all related through inheritance

Example:

Animal.java:


public class Animal {

public Animal() {

System.out.println("A new animal has been created!");

}


public void sleep() {

System.out.println("An animal sleeps...");

}


public void eat() {

System.out.println("An animal eats...");

}


}


Bird.java:


public class Bird extends Animal {

public Bird() {

super();

System.out.println("A new bird has been created!");

}


@Override

public void sleep() {

System.out.println("A bird sleeps...");

}


@Override

public void eat() {

System.out.println("A bird eats...");

}

}

  • Both classes Animal and Bird above are related to each other by inheritance
  • The class Animal is the superclass of the class Bird, and the class Bird is a subclass of the class Animal

Important Facts:

  • You can have an 'infinite' amount of subclasses
  • Each subclass can only extend to one superclass
  • Inheritance allows programmers to re-use code that they have already written
  • Subclasses can become superclasses over its own subclasses