Java 17 Quick Syntax Reference by Mikael Olsson

Author:Mikael Olsson
Language: eng
Format: epub
ISBN: 9781484273715
Publisher: Apress

// Subclass (child class)

class Apple extends Fruit

{

public String variety;

}

A class in Java may only inherit from one superclass, and if no class is specified, it will implicitly inherit from Object. Therefore, Object is the root class of all classes.// Same as class MyClass {}

class MyClass extends Object {}

Upcasting

Conceptually, a subclass is a specialization of the superclass. This means that Apple is a kind of Fruit, as well as an Object, and can therefore be used anywhere a Fruit or Object is expected. For example, if an instance of Apple is created, it can be upcast to Fruit because the subclass contains everything in the superclass.Apple a = new Apple();

Fruit f = a;

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