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

Language changes:

  • lambda expressions (JSR 335, includes method handles)
  • continuation of Project Coin (small language improvements)
  • annotations on Java types

Library changes:

Java 7 (a.k.a 1.7)

JSR 336, features and enhancements

Language changes:

  • Project Coin (small changes)

Library changes:

Platform 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 @Override).

Java 5 (a.k.a 1.5)

JSR 176, features and enhancements

Language Changes:

Library changes:

  • concurrency utilities in java.util.concurrent

Java 1.4

JSR 59

Language changes:

Library changes:

Java 1.3

Mostly minor improvements, really.

Platform changes:

  • HotSpot JVM: improvement over the original JIT

Java 1.2

Language changes:

Library changes:

Platform changes

  • a real JIT, greatly improving speed

Java 1.1

Language changes:

  • inner classes

Library changes:

  • AWT event changes
  • JDBC, RMI
  • reflection

Java 1.0

Initial release, everything is new ;-)