Indeed, if a Java Map implementation allows for null values, then it is possible for the Map to return its value for the given key, but that value might be a null.

In this quick tutorial on how the Java HashMap works internally, you'll learn the following aspects: The basic syntax of the Java HashMap. How keys, values, hash codes and node references interact.

How to add multiple values per key to a Java HashMap. It seems like an oversight for the standard Java API not to have a collection class that allows a key to have multiple values. If this is an ...