Here are some popular Java frameworks for building a fintech app:

1. Spring: A widely used Java framework that offers a comprehensive set of features for building enterprise-grade applications.

2. Quarkus: A relatively new, cloud-native, and low-latency framework specifically designed for microservices.

3. Micronaut: Another modern, cloud-native framework designed for building high-performance, low-memory-footprint microservices.

4. Vert.x: A reactive framework for building scalable, high-performance applications, particularly for web and microservices.

5. JavaServer Faces (JSF): A component-based framework for building Java-based web applications, with a focus on user interfaces.

These frameworks have strong communities and have been widely used in the industry for developing fintech applications, but the best one for you will depend on your specific requirements and development team's expertise.

Leading Java development company Narola Infotech recognizes the need of staying up to date with trends and advancements. To boost output and raise quality, our developers take care to fully use the new features. That explains why our clients are content working with us. Feel free to get in touch with our professionals whenever you have a Java project in mind.