A while back I wrote a generic comparator for Java objects and called it
GComp. We’ve been using it internally at the company where I work, but I was
wondering if it might not be of value to the commons project.
Typically Java programmers create a custom Comparator implementation for
every comparison scenario they encounter. GComp on the other hand can
compare objects according to complex criteria based on a simple expression
that explains how the objects should be compared. Great time saver and
prevents problem of many small comparator classes bloating the code base.
Usage scenario:
Lets say we have a class called Customer with methods to access the first
name and last name. Lets also say we have a class called Order that holds a
reference to an instance of Customer.
To compare orders according to the customer surname (ascending) we could
create the following comparator:
new GComp("getLastName");
To compare a collection of orders according to the customer last name
(ascending) and then first name (descending) for those customers with the
same last name we could create the following comparator:
new
GComp("[EMAIL PROTECTED]|[EMAIL PROTECTED]
");
To order null values last and ignore case we could create:
new
GComp("[EMAIL PROTECTED],nulls=last|getCustomer.
[EMAIL PROTECTED],nulls=last");
The above code only orders on string objects, but all objects implementing
the comparable interface is supported as is primitive types.
Currently GComp uses commons-logging to output debugging information if
commons logging is found on the classpath.
I'm happy to donate the code for further study. Let me know.
Keep well,
Wickus Martin
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