Overview of Java releases

This illustration highlights the changes that were introduced with each major Java release.

 
Here is a more detailed break down of the changes.

JDK 1.0 (1996)

• Initial release

JDK 1.1 (1997)

• Inner classes added
• Java Beans introduced
• RMI (Remote Method Invocation) added
• Initial (Windows) JIT compiler
• Reflection introduced - to reflect upon Class methods and fields
• Object serialization for sending objects over the network
• AWT (Abstract Window Toolkit) retooling for GUI enhancements
• JDBC (Java Database Connectivity) to enable connectivity and SQL query support
• Security enhancements - digital signatures, key signatures, access control lists

J2SE 1.2 (1998)

A slight re-branding was made from JDK to J2SE to properly distinguish from J2EE and J2ME.

• Collections framework added
• Keyword 'strictfp' added
• Real JIT compiler is included with JVM
• Swing API is integrated into core classes
• Java IDL (Interface description language) for CORBA interoperability
• Java plug-in added for Java applet support in web browsers

J2SE 1.3 (2000)

• HotSpot JVM included - encompassing JIT compilation and adaptive optimization to further improve performance
• Synthetic proxy classes - classes generated at runtime that are not in source code
• Java Naming and Directory Interface (JNDI) included in core libraries
• Java Platform Debugger Architecture (JPDA)
• RMI compatibility with CORBA
• JavaSound API

J2SE 1.4 (2002)

• JAXP (Java API for XML Processing) added; an XML parser and XSLT processor
• Regular expressions modeled after Perl
• Chained exceptions introduced
• IPv6 support added
• NIO (New I/O) introduced for intensive I/O operations
• Java Web Start
• Preferences API
• Logging API

J2SE 5.0 (2004)

• Generics added
• Annotations added
• Auto-boxing/unboxing added
• Enumerations - type safe, ordered list of values
• Varargs
• Enhanced for-each loop
• Static imports
• Scanner class: parses data from input streams and buffers
• Concurrency utilities
• Executor framework for invoking, scheduling and executing tasks
• Concurrent collections: concurrent implementations of Map, List, and Queue
• Atomic variable classes for atomically manipulating single variables 
• Synchronizers: semaphores, mutexes, barriers, latches, and exchangers

Java SE 6 (2006)

Going forward, Sun renamed the library to Java SE.

• JVM improvements: synchronization and compiler performance optimisations, garbage collection algorithms, and start-up performance
• GUI improvements
• Pluggable annotations allowing custom annotation processors
• JAXB v2.0 (XML Binding) and addition of StAX parser (pull streaming XML with write capability)
• JDBC v4.0 support
• JAX-WS (XML Web Services)
• Java Compiler API
• Scripting language support

Java SE 7 (2011)

• Strings in switch
• try-with-resources Statement for automatic close of resource
• Shorthand diamond operator <> for inferring generic type
• @SafeVarargs annotation for disabling compiler warning when vararg is a non-refiable
• Binary integer literals
• Underscores in numeric literals

Java SE 8 (2014)

• Lambda expressions (closures): an anonymous function that you can use to create delegates or expression tree types
• New Date and Time API
• Type annotations
• Repeating annotations
• Nashorn - lightweight high-performance JavaScript runtime

Read more at:
http://en.wikipedia.org/wiki/Java_version_history