Building robust and scalable web applications is not an easy task, but it is essential for the long-term success of any software project. Java has been one of the most popular programming languages for developing web applications for many years, and its robustness, scalability, and ability to handle complex applications have made it the language of choice for building web applications.

To build robust and scalable web applications with Java, here are ten tips that developers should consider:

1. Write Clean Code: Clean code is essential for the long-term success of any software project. Writing clean code involves using consistent naming conventions, keeping classes and methods concise, and avoiding code duplication.

2. Use Object-Oriented Design Principles: Object-oriented design principles, such as encapsulation, inheritance, and polymorphism, are essential for building scalable web applications. Object-oriented design makes it easier to manage the complexity of large applications and makes them more scalable.

3. Use Design Patterns: Using design patterns can improve the quality of your code and make it more maintainable. Some popular design patterns for web applications include the Model-View-Controller (MVC) pattern and the Singleton pattern.

4. Use a Framework: Using a framework can speed up your development process and provide you with a set of tools and conventions for developing web applications. There are many Java frameworks available for building web applications, including Spring, Struts, and Play.

5. Use a Build System: Using a build system, such as Maven or Gradle, can automate your build process and make it easier to manage dependencies. Build systems can also help you test your code and deploy your application.

6. Use a Database: Using a database can make your web application more scalable and reliable. Databases can handle large amounts of data and provide you with a powerful language for querying and manipulating data.

7. Use Caching: Caching can improve the performance of your web application by storing frequently accessed data in memory. Caching can reduce the load on your database and improve the speed of your web pages.

8. Use Monitoring and Logging: Monitoring and logging can help you detect and diagnose issues in your web application. Monitoring tools can provide you with real-time data on the performance and health of your application, while logging can record errors and exceptions for later analysis.

9. Use Testing: Testing is essential for building a robust and scalable web application. Testing can help you catch bugs before they reach production and ensure that your application behaves as expected. Some popular testing frameworks for Java web applications include JUnit and Selenium.

10. Use Continuous Integration and Deployment: Continuous integration and deployment can help you automate your build process and ensure that your application is always up-to-date. Continuous integration involves automatically building and testing your code whenever changes are made, while continuous deployment involves automatically deploying your code to production.

In conclusion, building robust and scalable web applications is a complex task that requires planning, research, and experience. Using Java and following these ten tips can help developers build web applications that are reliable, scalable, and high-performing.