Answers for "java nested class"

Nested classes in java

// example on inner class in java
class OuterDemo
{
   int num;
   // inner class
   private class InnerDemo
   {
      public void display()
      {
         System.out.println("inner class");
      }
   }
   // access inner class from method within
   void printInner()
   {
      InnerDemo objInner = new InnerDemo();
      objInner.display();
   }
}
public class InnerClassExample
{
   public static void main(String[] args)
   {
      OuterDemo objOuter = new OuterDemo();
      objOuter.printInner();
   }
}

Nested classes in java

// example on static nested classes java
import java.util.*;
public class OuterClass
{
   static class NestedClass
   {
      public void display() 
      {
         System.out.println("static nested class example");
      }
   }
   public static void main(String[] args) 
   {
      OuterClass.NestedClass nested = new OuterClass.NestedClass();	 
      nested.display();
   }
}

Nested classes in java

// anonymous inner class as method argument.
interface HelloWorld
{
   String print();
}
public class AnonymousInnerDemo
{
   // method accepts object of interface HelloWorld
   public void display(HelloWorld m)
   {
      System.out.println(m.print() + "example of anonymous inner class as method argument.");
   }
   public static void main(String[] args)
   {
      AnonymousInnerDemo obj = new AnonymousInnerDemo();
      // pass an anonymous inner class as an argument
      obj.display(new HelloWorld() {
         public String print() {
            return "Hi! ";
         }
      });
   }
}

Nested classes in java

// example on method local inner class in java.
class Outer
{
   // outer class instance method
   void display()
   {
      int num = 96;
      // method-local inner class
      class MethodLocalInner
      {
         public void show()
         {
            System.out.println("in method local inner class " + num);
         }
      } // end of inner class
      // access method local inner class
      MethodLocalInner objInner = new MethodLocalInner();
      objInner.show();
   }
   public static void main(String[] args)
   {
      Outer objOuter = new Outer();
      objOuter.display();
   }
}

inner class vs outer class

1. Can Outer class be static? --> No
2. Can inner class be static? --> Yes
3. Can you create an object from the inner class? --> Only if it's static
4. Can we have main method in inner class ? --> Only if it's static
5. Inner class can only be extended if it's static.

java nested class

class CPU {
    double price;
    // nested class
    class Processor{

        // members of nested class
        double cores;
        String manufacturer;

        double getCache(){
            return 4.3;
        }
    }

    // nested protected class
    protected class RAM{

        // members of protected nested class
        double memory;
        String manufacturer;

        double getClockSpeed(){
            return 5.5;
        }
    }
}

public class Main {
    public static void main(String[] args) {

        // create object of Outer class CPU
        CPU cpu = new CPU();

       // create an object of inner class Processor using outer class
        CPU.Processor processor = cpu.new Processor();

        // create an object of inner class RAM using outer class CPU
        CPU.RAM ram = cpu.new RAM();
        System.out.println("Processor Cache = " + processor.getCache());
        System.out.println("Ram Clock speed = " + ram.getClockSpeed());
    }
}