Question

This is a code i found for Egit

I am new to the usage of PlotCommitList<L extends PlotLane>.

1. what is the term used for it?
2. what does it signify or mean to the compiler?

public class PlotCommitList<L extends PlotLane> extends RevCommitList<PlotCommit<L>> {

Answer 1

The <> operator is used to specify classes in generic templates.

Image a generic “list”. In Java up to 1.4, a “list” could only contain generic Objects.
If you wanted to make sure you only kept Strings in your list you had to use a lot of casting and helper methods, which made the code barely readable.

Java 5 introduced generics, which solves the problem – you can create a template class “list of “, and parametrise the class used as parameter or return value.

Furthermore, you can use the <L extends ...> and <L super ...> to limit the range of classes your template works with, have multiple classes as parameters <class1,class2> and combine things up <class1,class2<class3>> at will.

There is a very good tutorial at http://www.javacodegeeks.com/2011/04/java-generics-quick-tutorial.html