An investigation of inner class behaviour. Prints information about a class and it's enclosing class.

Thing.java

/**
 * public domain
 * 
 * https://creativecommons.org/publicdomain/zero/1.0/
 * 
 */
package test;

import java.lang.reflect.Modifier;
import java.util.concurrent.Callable;

public class Thing implements Callable<String> {

    public static String whoami(Class<?> clazz) {
        return (Modifier.isStatic(clazz.getModifiers()) ? "static " : " ") + clazz.getName() + " : " + clazz.getEnclosingClass();
    }

    public final static Callable<String> STATIC_ANON = new Callable<String>() {
        @Override
        public String call() {
            Class<?> clazz = getClass();
            return whoami(clazz);
        }
    };

    public final Callable<String> INSTANCE_ANON = new Callable<String>() {
        @Override
        public String call() {
            Class<?> clazz = getClass();
            return whoami(clazz);
        }
    };

    public final static Callable<String> STATIC_STATIC = new Static();

    public static class Static implements Callable<String> {

        @Override
        public String call() {
            Class<?> clazz = getClass();
            return whoami(clazz);
        }
    };

    public final Callable<String> INSTANCE_STATIC = new Static();

    public final Callable<String> INSTANCE_INNER = new Inner();

    class Inner implements Callable<String> {

        @Override
        public String call() {
            Class<?> clazz = getClass();
            return whoami(clazz);
        }
    };

    public final static Callable<String> ASSOCIATED_STATIC = new Associated();

    public final Callable<String> INSTANCE_ASSOCIATED = new Associated();

    public final static Callable<String> ASSOCIATED_ANON_STATIC = new Associated() {

        @Override
        public String call() {
            Class<?> clazz = getClass();
            return whoami(clazz);
        }
    };

    public final Callable<String> INSTANCE_ANON_ASSOCIATED = new Associated() {

        @Override
        public String call() {
            Class<?> clazz = getClass();
            return whoami(clazz);
        }
    };

    @Override
    public String call() throws Exception {
        Callable<String> ANONYMOUS_INSTANCE = new Callable<String>() {

            @Override
            public String call() {
                Class<?> clazz = getClass();
                return whoami(clazz);
            }
        };

        return ANONYMOUS_INSTANCE.call();
    }

    public static void main(String... args) throws Exception {
        class Local implements Callable<String> {

            @Override
            public String call() {
                Class<?> clazz = getClass();
                return whoami(clazz);
            }

        }

        final Callable<String> LOCAL = new Local();

        final Callable<String> ANONYMOUS_STATIC = new Callable<String>() {
            @Override
            public String call() {
                Class<?> clazz = getClass();
                return whoami(clazz);
            }
        };

        Thing thing = new Thing();

        System.out.println("Thing: " + Thing.whoami(Thing.class));
        System.out.println("thing: " + Thing.whoami(thing.getClass()));
        System.out.println("STATIC_ANON: " + Thing.STATIC_ANON.call());
        System.out.println("INSTANCE_ANON: " + thing.INSTANCE_ANON.call());
        System.out.println("INSTANCE_STATIC: " + thing.INSTANCE_STATIC.call());
        System.out.println("INSTANCE_INNER: " + thing.INSTANCE_INNER.call());
        System.out.println("ASSOCIATED_STATIC: " + Thing.ASSOCIATED_STATIC.call());
        System.out.println("ASSOCIATED_ANON_STATIC: " + Thing.ASSOCIATED_ANON_STATIC.call());
        System.out.println("INSTANCE_ASSOCIATED: " + thing.INSTANCE_ASSOCIATED.call());
        System.out.println("INSTANCE_ANON_ASSOCIATED: " + thing.INSTANCE_ANON_ASSOCIATED.call());
        System.out.println("LOCAL: " + LOCAL.call());
        System.out.println("ANONYMOUS: " + ANONYMOUS_STATIC.call());
        System.out.println("ANONYMOUS_INSTANCE" + thing.call());
    }
}

class Associated implements Callable<String> {

    @Override
    public String call() {
        Class<?> clazz = getClass();
        return Thing.whoami(clazz);
    }
}

Output of revised version is:

run:
Thing:  test.Thing : null
thing:  test.Thing : null
STATIC_ANON: static test.Thing$1 : class test.Thing
INSTANCE_ANON:  test.Thing$2 : class test.Thing
INSTANCE_STATIC: static test.Thing$Static : class test.Thing
INSTANCE_INNER:  test.Thing$Inner : class test.Thing
ASSOCIATED_STATIC:  test.Associated : null
ASSOCIATED_ANON_STATIC: static test.Thing$3 : class test.Thing
INSTANCE_ASSOCIATED:  test.Associated : null
INSTANCE_ANON_ASSOCIATED:  test.Thing$4 : class test.Thing
LOCAL:  test.Thing$1Local : class test.Thing
ANONYMOUS: static test.Thing$6 : class test.Thing
ANONYMOUS_INSTANCE test.Thing$5 : class test.Thing