Sim Hui  Tee, 
    Developing a Maintainability Metric for Inner Classes,
    Asian Journal of Information Technology,
    Volume 9,Issue 2,
    2010,
    Pages 98-100,
    ISSN 1682-3915,
    ajit.2010.98.100,
    (https://makhillpublications.co/view-article.php?doi=ajit.2010.98.100)
    Abstract: Inner classes are widely used in some programming languages, such as Java. Inner classes are known as helper classes which are defined within outer class. They play the role to assist their outer class in performing a specific task. However, extensive use of inner classes may cause difficulty in software maintenance. This research proposes a maintainability metric for inner classes. The maintainability metric provides a guideline for software developers to define maintainable inner classes in an application.
    Keywords: Software maintainability;inner classes;object-oriented programming;software metric;outer classes;class complexity