Nested Class

Nested Class:
Java allows creating a class inside another class. These kinds of classes are called nested Class.
The simplest example for a nested class is:

 class OuterClass {  
 class ClassInside  
     {  
       //do something  
     }  
 }  

Why Use Nested Class:

There are several compelling reasons for using nested classes, among them:

• It is a way of logically grouping classes that are only used in one place.
• It increases encapsulation.
• Nested classes can lead to more readable and maintainable code.

Nested classes can be divided into two categories: Static & non-Static. The classes that are static are called Static Nested Class & the classes that are not static are called Inner Class.

---

 public class 
OuterClass {   
     String name = "Mc";   
 public String callName()   
     {   
  return name;   
     }   
 // Static nested class
 public static class NestedClass   
     {   
        String surname = "Donalds";   
  public String callSurname()   
        {   
   return surname;   
        }   
     }   
 // Inner Class
 public class InnerClass   
     {   
        String surname = "Donalds";   
  public String callSurname()   
        {   
    return surname;    
        }   
     }   
 }   
 //caller class   
 public class Caller {   
 public static void main(String args[]){   
        OuterClass oc = new OuterClass();   
        System.out.print(oc.callName()+" ");   
        // calling static class directly   
        OuterClass.NestedClass ic = new OuterClass.NestedClass();   
        System.out.println(ic.callSurname());   
        System.out.println("=================================================");   
        System.out.print(oc.callName()+" ");   
        // calling using object 
        OuterClass.InnerClass obj = oc.new InnerClass();   
        System.out.println(obj.callSurname());   
     }   
 }   

Inner Class:
We have already discussed about the Inner classes. Now, the inner classes can be defined into 3 categories:
1. Simple Inner Class (Non-static class)(Scope : Member  i.e. can be accessed by creating objects )
2. Local Class(Scope: Local)
3. Anonymous Class(Scope : Only at the point where it is defined)
Simple Inner Class: We have already discussed about the simple inner class. Once again the example for simple inner class:

 public class OuterClass {   
 // Simple Inner Class   
 public class InnerClass   
     {   
        String surname = "Donalds";   
  public String callSurname()   
        {   
   return surname;   
        }   
     }   
 }     

Local Class:
The inner classes that has no access specifier mentioned in it.

 public class OuterClass {  
 // Local Class  
 class InnerClass  
     {  
        String surname = "Donalds";  
  public String callSurname()  
        {  
   return surname;  
        }  
     }  
 }  

Anonymous Class:


“Anonymous class”- the name describes the class itself .That means, the class which doesn’t have a name. More technically, an anonymous class declaration is automatically derived from a class instance creation expression by the java compiler.
Anonymous class is -
1. Never ABSTRACT
2. Always IMPLICITLY FINAL
Example:

 //SuperClass   
 public class SuperClass {   
     SuperClass()   
     {   
 //do something   
     }   
 }   
 //called from this class   
 public class AnonymousCaller{   
 public static void main(String args[])   
     {   
        SuperClass sc =new SuperClass(){   
  public void method(){   
               System.out.println("TREE");   
               }   
        };   
        sc.method();   
     }   
 }   

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