Inner Class
In Java, one can define a new class inside any other class. Such classes are known as Inner class. It is a non-static class, hence, it cannot define any static members in itself. Every instance has access to instance members of containing class. It is of three types:
- Nested Inner Class
- Method Local Inner Class
- Anonymous Inner Class
Generally, it makes code slightly complicated but, it is very useful with abstract window toolkit and AWT(GUI) event handling.
Example:
Java
public class Outer { // outer class void showData() { // method inside outer class --- } public class Inner { // inner class inside outer class }} |
Sub Class
In Java, a subclass is a class that derives/inherited from another class. A subclass inherits everything (like behavior, state of the class, etc. ) from its ancestor classes. For a better understanding of it, we just need to know about the superclass. The superclass is an immediate ancestor of the sub-class. As a subclass has the property of inheriting the properties of an ancestor, hence, it can modify or override the methods of the superclass. For creating a subclass from any other class, we need to use extends clause in the class declaration.
Example :
Java
// super classpublic class Mahindra { public Mahindra() { System.out.println("I am super class"); }} // sub classpublic class Scorpio extends Mahindra { public Scorpio() { System.out.println("I am sub class"); }} |
Difference Table
The difference between the Inner class and sub-class are listed below:
|
Inner Class |
Sub Class |
|---|---|
| It is a class that is nested within another class. | It is a class that inherits from another class. |
| It can be accessed with the reference of the outer class. | No reference is required. It can be accessed directly without any reference to any class. |
| It is useful in performing encapsulation properties of OOPs and event handling in AWT(GUI). | It is beneficial in performing the inheritance property of object-oriented programming (OOPs). |
| It is used when the “has-a” relationship with its outer class is defined. | It is used when the “is-a” relationship is defined with its parent class. |
| It contains methods as per the requirement. | It must include the methods which are present in the parent class. Also, it can include any other methods too as per the need. |
| It is always present in the same file where the outer class is present. | It may or may not be available in the same file/package as its parent class. |
| It cannot define any static methods inside it. | It contains all types of methods either static or non-static. |
