Java SE 7

http://www.oracle.com/technetwork/java/javase/jdk7-relnotes-418459.html#changes

Type Inference for Generic Instance Creation

You can replace the type arguments required to invoke the constructor of a generic class with an empty set of type parameters (<>) as long as the compiler can infer the type arguments from the context. This pair of angle brackets is informally called the diamond.

For example, consider the following variable declaration:

Map<String, List<String>> myMap = new HashMap<String, List<String>>();

In Java SE 7, you can substitute the parameterized type of the constructor with an empty set of type parameters (<>):

Map<String, List<String>> myMap = new HashMap<>();

http://www.eclipse.org/jdt/ui/r3_8/Java7news/whats-new-java-7.html