Android: understanding R.Java

Understanding the R.Java class in Android: What is R.Java ??


The Eclipse ADT automatically generates a R.java, which keeps track of all the application resources, in hello\gen as follows:

package com.mytest;
   
public final class R {
    public static final class attr {
    }
    public static final class drawable {          // Inner class R.drawable
        public static final int icon=0x7f020000;  // Resource ID R.drawable.icon
    }
    public static final class id {                // Inner class R.id
        public static final int textview=0x7f050000;  // Resource ID R.id.textview
    }
    public static final class layout {            // Inner class R.layout
        public static final int main=0x7f030000;  // Resource ID R.layout.main
    }
    public static final class string {            // Inner class R.string
        public static final int app_name=0x7f040001; // Resource ID R.string.app_name
        public static final int hello=0x7f040000;    // Resource ID R.string.hello
    }
}

The R.java (R stands for resources) indexes all the resources used in this application in the inner classes attr, drawable, id, layout, and string. 
For example, 
the inner class layout's property main (R.layout.main) references res\layout\main.xml; 
the inner class string references res\values\strings.xml; 
the inner classdrawable's property icon references res\drawable\icon which keeps the images used as icons in "apps" menu.