Java 7 focused on performance improvements and simplifying coding syntax with features like Try-with-resources and Multicatch Exception Handling.
Java 8 introduced functional programming, Lambda Expressions, Stream API, Optional class, Default and Static Methods in Interfaces, and modernized syntax.
Major features from Java 9 to Java 21 include New HTTP Client, Records, Pattern Matching, Long-Term Support, Sealed Classes, Virtual Threads, and more.
Transition tips include updating dependencies, using streams and lambdas, adopting var and records, and upgrading to newer Java versions for improved security and performance.