In other words, it was impossible to have a key be in the map without having a corresponding non-null value. package dustin.examples; import java.util.EnumMap; import java.util.HashMap ...

And, of course, when we put things into a HashMap, it's always a key-value pair, right? It's always two things. So, here's how the Java Virtual Machine gets around that. It creates its own class ...

Java collection classes allow a developer to keep track of contained items in one of two ways, either by an indexed count or a key. This creates an obvious limitation where multiple values can’t be ...