Question about the "Getting in Touch with your Inner Class" campfire tutorial

[Jeff Cortez]

Hi. I'm trying to understand inner and nested classes and have started by reading the "Getting in Touch with your Inner Class" campfire tutorial:

http://www.javaranch.com/campfire/StoryInner.jsp

I compiled the classes Outer and TestMe and ran TestMe with the correct output.
Immediately under that example, the tutorial goes on to say:

You can also instantiate both the outer class and inner class at the same time:

Inner i = new Outer().new Inner();

So, in class TestMe I commented out these two lines:

// Outer o = new Outer();
// Outer.Inner i = o.new Inner();

And inserted this line instead:

Inner i = new Outer().new Inner();

However, now class TestMe does not compile.
I then changed the statement to this:

Outer.Inner i = new Outer().new Inner();

The class TestMe again compiles and runs with the correct output.
Am I misunderstanding something in the campfire tale, or is this statement in the tutorial a bug? That is, Inner i needs to be changed to Outer.Inner i in the code snippet below.

You can also instantiate both the outer class and inner class at the same time:

Inner i = new Outer().new Inner();

Thanks.

[fred rosenberger]

Instead of saying "the class does not compile", please tell us the exact text of what it does say. Having that text makes it MUCH easier for folks to help you.

[Jeff Cortez]

Hi. In a file TestMe.java I have two class declarations TestMe and Outer. I commented out these two lines in TestMe:

//    Outer o = new Outer();
//Outer.Inner i = o.new Inner();

And inserted this from the tutorial:

Inner i = new Outer().new Inner();

class TestMe
{

    public static void main( String args[] ) 
    {
        // instantiate me, the outer object
        //    Outer o = new Outer();

        // Inner i = new Inner();
        // NO! Can't instantiate Inner by itself!

           Inner i = new Outer().new Inner();

        //Outer.Inner i = o.new Inner();
        // now I have my special inner object
        i.doStuff();
        // OK to call methods on inner object
    }

}


class Outer
{
    private int size ;
    private String thoughts = "My outer thoughts";

    class Inner
    {
        String innerThoughts = "My inner thoughts";

        void doStuff()
        {
            // inner object has its own "this" 
            System.out.println( innerThoughts );

            // and it also has a kind of "outer this"
            // even for private data of outer class
            System.out.println(thoughts);
        }
    }
} 

When I try to compile the file, I get this compiler error message:

TestMe.java:12: cannot find symbol
symbol : class Inner
location: class TestMe
Inner i = new Outer().new Inner();
^
1 error


My question is whether this statement in the campfire tutorial:

Inner i = new Outer().new Inner();

should instead be changed to this:

Outer.Inner i = new Outer().new Inner();

Thanks.

[fred rosenberger]

hmm...you may be right.

[Jeff Cortez]

Cool...gaining some Java traction. Thanks Fred!

[Campbell Ritchie]

Agree; the name of the class is Outer.Inner, not Inner, unless you are already inside the Outer class.

[Jeff Cortez]

Thank you Campbell!