Inheritance Explained

Inheritance is a concept in object-oriented programming (OOP) that allows a class to inherit properties and methods from another class. The class that is being inherited from is called the base class or the parent class, and the class that is inheriting from it is called the derived class or the child class.

The idea behind inheritance is that a derived class can reuse code from the base class, and can also add its own code on top of it. This can help to reduce code duplication and increase code reusability.

When a derived class inherits from a base class, it automatically gets all the properties and methods of the base class. The derived class can then override or extend these properties and methods as needed.

Inheritance in programming, especially in a language like Java, is like family inheritance in real life, but instead of inheriting properties like houses or jewelry, classes in programming inherit characteristics like methods and variables.

Inheritance in Java is a principle of Object-Oriented Programming (OOP) that allows one class to inherit properties and methods from another class. This functionality enables programmers to create new classes that reuse, extend, and modify the behavior defined in other classes.

Here’s a simple way to understand it:

Parent and Child Classes: Think of a parent class (also called a superclass) and a child class (subclass). The child class inherits or gets traits from the parent class, much like a child might inherit eye color or hair color from their parents.
Reusing Code: Just like how you might inherit a piece of furniture that's been in the family for generations, in programming, a child class can use methods and variables that were defined in its parent class. This is a way to reuse code, which saves time and effort.
Adding Unique Traits: While a child inherits traits from their parents, they also have their own unique traits. Similarly, in programming, a subclass can have its own unique methods and variables in addition to what it inherits from the parent class.
Overriding Inherited Traits: Sometimes, a child might want to change something they inherited, like repainting that inherited piece of furniture. In programming, this is called overriding. A subclass can override methods from the parent class to behave differently in the context of the subclass.
Hierarchy: Just like families can have multiple generations, programming can have multiple levels of inheritance. A class can inherit from another class, which in turn inherits from another class, and so on.
Polymorphism: Inheritance allows for polymorphism (we will cover in the next module), which in simple terms means that a subclass can be treated as if it's an instance of the parent class. This is similar to how a child might be seen as part of their family lineage.

In summary, inheritance in programming allows classes to inherit and share code, just like how family members might share physical traits or possessions. It's a fundamental concept in object-oriented programming that helps in organizing and structuring code efficiently.

Here are the key terms and concepts involved:

Superclass (or Parent class): This is the class from which another class inherits properties and methods.
Subclass (or Child class): This is the class that inherits properties and methods from another class. A subclass can also add new fields and methods, or it can override the methods of the superclass.
Inheritance: Inheritance represents the IS-A relationship, also known as parent-child relationship.

When a subclass inherits from a superclass, it gets:

All the non-private fields and methods from the superclass.
If a superclass does not have a no-arg (no argument) constructor, the compiler requires an explicit call to a superclass's constructor in each subclass constructor.
The subclass can still define its own fields and methods, including methods that have the same name as methods in the superclass (which is known as method overriding).
The subclass can also have its own constructors.

The key benefit of inheritance is that it allows for code reuse. Instead of writing the same code over and over again for similar objects, you can create a general class that includes common features and then create more specific classes that inherit from the general class while adding unique features of their own.

Java only supports single inheritance (a class can only inherit from one superclass), but it supports multiple levels of inheritance (where a class inherits from a subclass which inherits from another subclass and so on). Multiple inheritance is not supported in Java because of the "Diamond Problem," which can lead to ambiguity when a class would inherit from two classes that have a method with the same name.

Finally, remember that Java provides a mechanism to prevent a class from being inherited, by using the keyword final. When a class is declared as final, it cannot be subclassed. This is often done for reasons of security or efficiency.

Real-life objects are typically specialized versions of other more general objects.
The term “insect” describes a very general type of creature with numerous characteristics.
Grasshoppers and bumblebees are insects
- They share the general characteristics of an insect.
- However, they have special characteristics of their own.
  - grasshoppers have a jumping ability, and
  - bumblebees have a stinger.
Grasshoppers and bumblebees are specialized versions of an insect.

The “is a” relationship

The relationship between a superclass and an inherited class is called an “is a” relationship.
- A grasshopper “is a” insect.
- A poodle “is a” dog.
- A car “is a” vehicle.
A specialized object has:
- all of the characteristics of the general object, plus
- additional characteristics that make it special.
In object-oriented programming, inheritance is used to create an “is a” relationship among classes
We can extend the capabilities of a class.
Inheritance involves a superclass and a subclass.
- The superclass is the general class and
- the subclass is the specialized class.
The subclass is based on, or extended from, the superclass.
- Superclasses are also called base classes, and
- subclasses are also called derived classes.
The relationship of classes can be thought of as parent classes and child classes.