if (!Collection.class.isAssignableFrom(parameterTypes[index]) || !isParameterized(index)) {
            return null;
        }
        final ParameterizedClassDesc pcd = parameterizedClassDescs[index].getArguments()[0];
        if (pcd == null) {
            return null;
        }
        return pcd.getRawClass();
    }

    @Override
    public Class<?> getKeyClassOfMap(final int index) {

        if (!Collection.class.isAssignableFrom(parameterTypes[index]) || !isParameterized(index)) {
            return null;
        }
        final ParameterizedClassDesc pcd = parameterizedClassDescs[index].getArguments()[0];
        if (pcd == null) {
            return null;
        }
        return pcd.getRawClass();
    }

    @Override
    public Class<?> getKeyClassOfMap(final int index) {

        ParameterizedClassDesc pcd = pd.getParameterizedClassDesc();
        assertThat(pcd.getRawClass(), is(sameClass(Map.class)));
        assertThat(pcd.getArguments().length, is(2));
        assertThat(pcd.getArguments()[0].getRawClass(), is(sameClass(String.class)));
        assertThat(pcd.getArguments()[1].getRawClass(), is(sameClass(Date.class)));

        pd = bd.getPropertyDesc("hege");
        assertThat(pd.isParameterized(), is(true));

     * </p>
     *
     * @return 型引数を表す{@link ParameterizedClassDesc}の配列
     * @see ParameterizedType#getActualTypeArguments()
     */
    ParameterizedClassDesc[] getArguments();

        if (!Collection.class.isAssignableFrom(fieldType) || !isParameterized()) {
            return null;
        }
        final ParameterizedClassDesc pcd = parameterizedClassDesc.getArguments()[0];
        if (pcd == null) {
            return null;
        }
        return pcd.getRawClass();
    }

    @Override
    public Class<?> getKeyClassOfMap() {

        assertThat(desc.getRawClass(), is(sameClass(Map.class)));

        final ParameterizedClassDesc[] args = desc.getArguments();
        assertThat(args.length, is(2));

        final ParameterizedClassDesc arg1 = args[0];
        assertThat(arg1.getRawClass(), is(sameClass(String.class)));
        assertThat(arg1.getArguments(), is(nullValue()));

        final ParameterizedClassDesc arg2 = args[1];

        if (!Collection.class.isAssignableFrom(propertyType) || !isParameterized()) {
            return null;
        }
        final ParameterizedClassDesc pcd = parameterizedClassDesc.getArguments()[0];
        if (pcd == null) {
            return null;
        }
        return pcd.getRawClass();
    }

    @Override
    public Class<?> getKeyClassOfMap() {

        this.rawClass = rawClass;
    }

    @Override
    public ParameterizedClassDesc[] getArguments() {
        return arguments;
    }

    /**
     * 型引数を表す{@link ParameterizedClassDesc}の配列を設定します。
     *
     * @param arguments
     *            型引数を表す{@link ParameterizedClassDesc}の配列
     */
    public void setArguments(final ParameterizedClassDesc[] arguments) {
        this.arguments = arguments;
    }

        for (final Indexed<Type> parameterType : indexed(iterable(parameterTypes))) {
            parameterDescs[parameterType.getIndex()] = createParameterizedClassDesc(parameterType.getElement(), map);
        }
        desc.setArguments(parameterDescs);
        return desc;
    }

        for (int i = 0; i < parameterTypes.length; ++i) {
            parameterDescs[i] = createParameterizedClassDesc(parameterTypes[i], map);
        }
        desc.setArguments(parameterDescs);
        return desc;
    }