Get started with polymorphism in Java and how to do method invocation in polymorphic method calls.

Need to add multiple values to a key in a Java HashMap but can't figure out how to do it? Here are three examples of how to solve the multiple values per key problem in Java.

If you’ve read my Java 101 tutorial introducing static classes and inner classes, you should be familiar with the basics of working with nested classes in Java code. In this associated tip, I ...