no static method in inner class - why ?

[ankur rathi]

class Outer{
 class Inner {
 }
}

after compilation there will be two class files : Outer.class & Outer$Inner.class

When we will run this inner class with java Outer$Inner command this will give an error NoSuchMethodExist . Because it doesn't have a main method .And we can't have a main method in inner class because this method has static in its signature .

Now my question is why inner class can't have static methods ???

thanks a lot .
[ January 13, 2005: Message edited by: rathi ji ]

[Barry Gaunt]

You must never use the generated Outer$Inner.class file. In the case of your class and it's inner class you must have an instance of the outer class to be able to create an instance of its inner class.

"why inner class can't have static methods ???"

Because the JLS 8.1.2 says they can't.

And the Java Tutorial says
"Also, because an inner class is associated with an instance, it cannot define any static members itself."
[ January 13, 2005: Message edited by: Barry Gaunt ]

[Edwin Dalorzo]

You can do this:

public class Outer 
{
  static class Inner
  {
    public static void main(String args[])
    {
      System.out.println("Hello from inner class");
    }
  }
}

The outer class can be an instance class and the nested class could be static. This way you can implement static void main in the nested class and it will run.

[Mike Gershman]

But remember, a static nested class is not an inner class.