static nested class

[sridhar row]

source: self

  /*creating an static nested class object from outside the outer class instance code*/
 
class MyOuter{
   private int x = 10;
  
  static class MyInner{
    private int y =20;
    public void seeOuter(){
      System.out.println("Outer class variable x: "+new MyOuter().x);
    }
    public int getInnerInstance(){
      return this.y;//line 1 
    }
    public int getOuterInstance(){
      return new MyOuter().x;
    }
  }
}
 
public class InnerTest2{
  public static void main(String[] args){
    MyOuter.MyInner oi = new MyOuter.MyInner();//line 2    
    oi.seeOuter();
    System.out.println("Inner class variable y: "+ oi.getInnerInstance());
    System.out.println("Outer class variable x: "+ oi.getOuterInstance());
  }
}  

Hi folks,
I have a couple of questions from the above code i wrote. Can someone
1.tell me if there is any other way i can access outer class instance variable from inner class other than shown above.
2.explain line 2 and
3.in line 1 why am i not getting compiler error: non-static variable this cannot be referenced from a static context. Thanks

[Amit Ghorpade]

Hi,

I have a couple of questions from the above code i wrote. Can someone
1.tell me if there is any other way i can access outer class instance variable from inner class other than shown above.
2.explain line 2 and
3.in line 1 why am i not getting compiler error: non-static variable this cannot be referenced from a static context.

1. No there is no other way to access the outer class instance variable because the nested class is static
2. It is the proper way of instantiating a nested class.
3. It is because the nested class is static, and the member is an instance variable.



Hope this helps

[Dinesh Tahiliani]

Can you little elaborate...

[Dinesh Tahiliani]

class MyOuter
{   
private int x = 10; 
static class MyInner 
{   
private int y =20; 
public void seeOuter()
{   
System.out.println("Outer class variable x: "+ new MyOuter().x);  
}    
public int getInnerInstance()
{     
return y;//line 1  }    

/*public int getOuterInstance()
{      return new MyOuter().x;    
}*/ 
}
} 
public class InnerClass2
{ 
public static void main(String[] args)
{ 
MyOuter.MyInner oi = new MyOuter.MyInner();//line 2    
oi.seeOuter(); 
System.out.println("Inner class variable y: "+ oi.getInnerInstance());  
System.out.println("Outer class variable x: "+ oi.getOuterInstance()); 
}
  
}

You can also access the instance variable of inner class without this.I have tried and code complies fine.

output
Outer class variable x: 10
Inner class variable y: 20

Can you please tell me why you have used this at line 2 in your code to access the 'y' varaiable of Inner class.

[sridhar row]

Thanks Amit for the reply. I know it is the correct way. What I'm asking is why is it the correct way and can you explain whats happening here: MyOuter.MyInner oi = new MyOuter.MyInner();<--explain this line.

[Amit Ghorpade]

MyOuter.MyInner oi = new MyOuter.MyInner();<--explain this line.

yes, here you are instantiating a static nested class. As you know, nested classes are simply members of the class like other members.
say for example you need to access any static member of a class then you say
ClassName.staticMember. similarly in above code you access the static nested class constructor.
For inner classes, since thy are bound to instances, you need to say something like outerClassObj.MyInner()



Hope this helps