This is a summary of the excellent Wikipedia article about the Java version history. It is highly selective (and biased on what I know and use), otherwise it would simply turn out to be a copy of the article.
The bold parts are what really brought the language forward as a whole. As you see, not every release has bold parts.
Java 8 (a.k.a 1.8)
JSR 337, what's new
- lambda expressions (JSR 335, includes method handles)
- continuation of Project Coin (small language improvements)
- annotations on Java types
Java 7 (a.k.a 1.7)
JSR 336, features and enhancements
- Project Coin (small changes)
Java 6 (a.k.a 1.6)
JSR 270. features and enhancements
Mostly incremental improvements to existing libraries, no new language features (except for the
Java 5 (a.k.a 1.5)
JSR 176, features and enhancements
- concurrency utilities in
Mostly minor improvements, really.
- HotSpot JVM: improvement over the original JIT
- a real JIT, greatly improving speed
- AWT event changes
- JDBC, RMI
Initial release, everything is new ;-)