Instantiating Local Classes

[Vishnu Khera]

interface IDrawable {                   // (1)
  void draw();
}
//**********************************************
class Shape implements IDrawable {      // (2)
  public void draw() { System.out.println("Drawing a Shape."); }
}
//**********************************************
class Painter {                         // (3) Top-level Class
  public Shape createCircle(final double radius) { // (4) Non-static Method
    class Circle extends Shape {        // (5) Non-static local class
      public void draw() {
        System.out.println("Drawing a Circle of radius: " + radius);
      }
    }
    return new Circle();                // (6) Object of non-static local class
  }

  public static IDrawable createMap() { // (7) Static Method
    class Map implements IDrawable {    // (8) Static local class
      public void draw() { System.out.println("Drawing a Map."); }
    }
    return new Map();                   // (9) Object of static local class
  }
}
//*********************************************
public class LocalClassClient {
  public static void main(String[] args) {
    IDrawable[] drawables = {           // (10)
        new Painter().createCircle(5),  // (11) Object of non-static local class
        Painter.createMap(),            // (12) Object of static local class
        new Painter().createMap()       // (13) Object of static local class
    };
  }
}

The above code is from a book. I'm unable to understand what the author means by " In the non-static method, the reference to the instance of the enclosing context is passed implicitly in the constructor call of the non-static local class at (6). "

[Seetharaman Venkatasamy]

Inner Story (<= click) .

download a good decompiler (for example jad) , and open the inner classes. surprisingly you can find a different default constructor !

[Vishnu Khera]

Seetharaman I looove campfire stories Liked the Pass-by-value Please story

Thanks for sharing the link and for your response

Downloaded JD-GIU (a java decompiler) and decompiled the following code :

class OutOfTheBox {   
}

class Outer {
    int x,y;
    class Inner {
        int r, t;
    }
    public OutOfTheBox method() {
        class InsideMethod extends OutOfTheBox {
        }
        return new InsideMethod();
    }
}

class TestH {
    public static void main(String[] args) {
        Outer o = new Outer();
        Outer.Inner i = o.new Inner();
        o.method();
    }
}

FOUND THIS :

class Outer$1InsideMethod extends OutOfTheBox
{
  Outer$1InsideMethod(Outer paramOuter)
  {
  }
}

class Outer$Inner
{
  int r;
  int t;

  Outer$Inner(Outer paramOuter)
  {
  }
}

Now my question is - is there some specification about how class files would be named once we define inner classes - like it shows $ as a seperator; and $1 as a seperator for local classes?

[Mala Gupta]

Vishnu,

Now my question is - is there some specification about how class files would be named once we define inner classes - like it shows $ as a seperator; and $1 as a seperator for local classes?

$ followed by an integer is used for local classes because you can declare multiple local classes with the same name, in different methods. The following code adds a definition of local class 'InsideMethod' in 'method2()':

class Outer {
    int x,y;
    class Inner {
        int r, t;
    }
    public OutOfTheBox method() {
        class InsideMethod extends OutOfTheBox {}
        return new InsideMethod();
    }
    public OutOfTheBox method2() {
        class InsideMethod extends OutOfTheBox {}
        return new InsideMethod();
    }
}

When you compile the above class, the Java compiler will generate the following class files for the local inner classes 'InsideMethod' defined in 'method()' and 'method2()':

Outer$1InsideMethod.class
Outer$2InsideMethod.class

With respect,
Mala

[Vishnu Khera]

Thanks for your response Mala

[Abdullah mohammad]

Seetharaman Venkatasamy wrote:Inner Story (<= click) .

download a good decompiler (for example jad) , and open the inner classes. surprisingly you can find a different default constructor !

[Vishnu Khera]