Simple example of using method reference with Java 8
The Application.main creates a FirstClass and a SecondClass instances,
then call the second.applyFunction with the method first.addPrefix as argument.
Here java.util.function.Function is used as function-type argument:
a function with one generic argument and a generic output. Look at java.util.function for other function-type:
http://docs.oracle.com/javase/8/docs/api/java/util/function/package-summary.html