If you are starting with Neural Networks you should check out my online book on the subject. It contains over 300 pages of information on Neural Network Programming in Java. You can access it here.
D. Lee, S. Yu, and H. Yu. Proceedings of the 26th ACM SIGKDD International Conference on Knowledge Discovery & Data Mining, page 1362–1370. New York, NY, USA, Association for Computing Machinery, (2020)