1. Learn JVM Internals and Java Performance Tuning

If you are serious about becoming a Rockstar Java Developer then you must first spend the time to learn JVM internals like what are different parts of JVM, how they work, JIT, JVM options, Garbage collections, and collectors, etc.

If you know the JVM well you can write both robust and high-performance Java application and that’s what Rockstar Java developers do. As part of this, you should also learn how to profile your Java application, how to find performance bottlenecks like which objects are taking most of your memories, and eating CPUs.

2. Learn Microservices and Cloud

Architecture is changing constantly and many companies are moving from monolithic applications to microservices.
It’s high time for Java developers to learn Microservice architecture and how to create Microservices in Java to take advantage of this recent wave.

Fortunately, the Spring framework provides Spring Cloud and Spring Boot which greatly simplify microservice development in Java. If you are looking for a course then Master Microservices with Spring Boot and Spring Cloud is a good one to start with.

3. Learn Spring Framework (Spring Boot)

It’s almost imperative nowadays for a Java developer to learn Spring framework as most of the companies prefer to do development using Spring frameworks like Spring MVC, Spring Boot, and Spring Cloud for developing a web application, REST APIs, and Microservices.

It also promotes best practices like dependency injection and makes your application more testable which is a key requirement for modern-day software.

4. Learn Java APIs and Libraries

If you have worked with great Java developers you might have noticed their overall knowledge of the Java Ecosystem and APIs forms a major part of it.

Java is the world’s most popular and mature programing language and there are tons of libraries and APIs available for doing almost everything possible.

Of course, you are not expected to know all of them but you should be familiar with some key APIs like JSON processing APIs like Jackson and Gson, XML processing APIs like JAXB and Xerces, Unit testing libraries like Mockito and JUnit, etc.

5. Learn Java 8+ (Java 13)

This is the most important thing for a Java developer right now. It’s good 4 years old and even Java 13 has been released 6 months back.

Almost all Java development jobs now required Java 8 skills and if you don’t have them, it would be very difficult to do well and perform well in your Java interviews.

6. Learn Design Patterns and Coding Best Practices

If you are writing a Java application from scratch then most of the time you are writing object-oriented code and design patterns are tried and tested solutions of common problems.

By knowing and incorporating them into your code you make your application more flexible and easier to change in the future.