AspectJ
AspectJ is an aspect-oriented extension of the Java programming language that allows developers to modularize crosscutting concerns. It is mainly used for implementing aspects, which enable the separation of crosscutting concerns from the main business logic in Java applications.
Popularity: Less than 1% of developers are using or have used this language.*
*According to StackOverflow's 2023 survey.
Repositories on GitHub: 690