1. Java Programming: A strong grasp of the Java programming language is fundamental. This includes understanding core concepts such as object-oriented programming (OOP), data types, variables, control structures, and exception handling.

2. Frameworks and Libraries: Familiarity with popular Java frameworks and libraries like Spring, Hibernate, JavaFX, etc., is essential for building robust and efficient applications.

3. Database Management: Knowledge of working with databases and SQL is crucial for many applications. Understanding how to interact with databases through Java and manage data effectively is essential.

4. Web Development: Java developers often work on web applications, so expertise in web technologies like HTML, CSS, and JavaScript, along with frameworks like Spring MVC, is beneficial.

5. Version Control: Proficiency with version control systems like Git is essential for collaborative development and code management.

6. IDEs (Integrated Development Environments): Familiarity with Java IDEs like Eclipse, IntelliJ IDEA, or NetBeans is important to enhance productivity and facilitate code debugging.

7. Testing and Debugging: Knowledge of unit testing frameworks (e.g., JUnit) and debugging tools is critical to ensure code quality and identify and fix issues efficiently.

8. Concurrency and Multithreading: Understanding how to write concurrent and thread-safe code is crucial for building scalable applications.

9. Design Patterns: Knowledge of common design patterns and how to apply them in Java can help you write maintainable and reusable code.

10. Java Virtual Machine (JVM) Internals: A deeper understanding of how the JVM works can help you optimize performance and troubleshoot issues in Java applications.

11. Build Tools: Experience with build automation tools like Maven or Gradle simplifies the process of managing dependencies and building projects.

12. Security: Awareness of secure coding practices and methods to mitigate common security vulnerabilities is important, especially for web-based applications.

13. Problem-Solving and Algorithmic Skills: As with any programming role, strong problem-solving skills and knowledge of data structures and algorithms are valuable for writing efficient and optimized code.

14. Continuous Learning: The tech industry is constantly evolving, so being open to learning new tools, technologies, and best practices is essential to stay up-to-date and improve your skills.

15. Teamwork and Communication: Collaborating effectively with team members and stakeholders, and being able to communicate technical concepts clearly are essential soft skills for any developer.

Remember that Java development is a vast field, and specific projects or positions may require additional or more specialized skills. Stay curious and open to learning, and continuously improve your skills to excel as a Java developer.