Refreshing my knowledge of Java so that I'm not falling behind.

Main features after Java 8

• Collection factory methods (Java 9)
• Private methods in interfaces (Java 9)
• New Optional methods (Java 9)
• Local type inference (Java 10)
• New String methods (Java 12)
• New switch (Java 13)
• New instanceof (Java 14)
• The record keyword (Java 14)
• sealed classes and interfaces (Java 15)
• The text block (Java 15)

Advanced Topics

• Annotation
• Generic
• IO
• NIO
• Serialization/Deserialization

References

• Effective Java (3rd Edition).