1. Initially released in September 2004.
2. Has 3200+ classes and interfaces.
3. Introduced several updates and improvements
Annotations:- Anotations wrere used to provide meta-data for the programs so that it can be easily understand for metadata-aware programs.
Generics:-Generics are used to provide types of object belonging to collections. So that type safety cab be gauranteed at compile time.
Autoboxing :- Autoboxing is used to automatically convert from primitive types to wrapper clsses.
Improved syntax for looping :-Improved syntax of loops was introduced like for each loop
Varargs :- Provide flexibility to pass variable no of arguments. Look Here