In this Java 101 tutorial, I’ve explained how interfaces differ from classes, and showed you how to declare, implement, and extend interfaces in your Java programs.

Create packages, import packaged classes and interfaces into your programs, move packages, and encapsulate them in jar files.

If you want to take advantage of sorting methods in Java, you'll need to implement the Comparable interface.

While languages like Ruby provide the pertinent information you need, why can't Java provide a decent, useable, toString() method right out of the box?