I remember when I was attending Java training in my organization our trainer told us the Sun Microsystems (now Oracle) launched a new version of Java Java SE 7 and its code name is Dolphin .At that time I was very surprise because I was working in Java from last 3 year and I did not know this thing that every version of Java has its own significance and its own code name too.

After that I was curious to all the "code name" so I founded it out. Here I am sharing this information with you guys . It will be a good learning experience.

I have summarized below important new features added in each major Java release till now. I target to highlight important features added in respective releases. Apart from below list of features, every release has enhancements too.

Java Version SE 7
code named Dolphin and released on July 28, 2011.

New features in Java SE 7

• Strings in switch Statement
• Type Inference for Generic Instance Creation
• Multiple Exception Handling
• Support for Dynamic Languages
• Try with Resources
• Java IO Package
• Binary Literals, underscore in literals
• Diamond Syntax
• Automatic null Handling    

Java Version SE 6
Code named Mustang and released on December 11, 2006.

New features in Java SE 6

• Scripting Language Support
• JDBC 4.0 API
• Java Compiler API
• Pluggable Annotations
• Native PKI, Java GSS, Kerberos and LDAP support.
• Integrated Web Services.
• Lot more enhancements.

J2SE Version 5.0
Code named Tiger and released on September 30, 2004.

New features in J2SE 5.0

• Generics
• Enhanced for Loop
• Autoboxing/Unboxing
• Typesafe Enums
• Varargs
• Static Import
• Metadata (Annotations)
• Instrumentation

J2SE Version 1.4
Code named Merlin and released on February 6, 2002 (first release under JCP).

New features in J2SE 1.4

• XML Processing
• Java Print Service
• Logging API
• Java Web Start
• JDBC 3.0 API
• Assertions
• Preferences API
• Chained Exception
• IPv6 Support
• Regular Expressions
• Image I/O API

J2SE Version 1.3
Code named Kestrel and released on May 8, 2000.

New features in J2SE 1.3

• Java Sound
• Jar Indexing
• A huge list of enhancements in almost all the Java area.

J2SE Version 1.2
Code named Playground and released on December 8, 1998.

New features in J2SE 1.2

• Collections framework.
• Java String memory map for constants.
• Just In Time (JIT) compiler.
• Jar Signer for signing Java ARchive (JAR) files.
• Policy Tool for granting access to system resources.
• Java Foundation Classes (JFC) which consists of Swing 1.0, Drag and Drop, and Java 2D class libraries.
• Java Plug-in
• Scrollable result sets, BLOB, CLOB, batch update, user-defined types in JDBC.
• Audio support in Applets.

JDK Version 1.1
Released on February 19, 1997
New features in JDK 1.1

• JDBC (Java Database Connectivity)
• Inner Classes
• Java Beans
• RMI (Remote Method Invocation)
• Reflection (introspection only)

JDK Version 1.0

Code named Oak and released on January 23, 1996.