Combining Java enums with dot syntax (enum.value1.value2)?

Question

I'm going through some existing (and working) code and came across a line like this:

if (someObject.getStatus() == SomeEnum.VALUE1.VALUE2) { ... }

Where SomeEnum is a simple enum that looks like this:

public enum SomeEnum {
    VALUE1,
    VALUE2,
    VALUE3,
    ...
}

private SomeEnum() {}

Now, what does that comparison above do? More precisely, what does the combination of two enum values in there do? I was astonished to not see any warnings or errors because of that line as I assumed this was simply wrong. However, it compiles and runs just fine. Can someone enlighten me on what this would do?

Answer 1

You should get a warning about this if you're using an IDE like Eclipse, saying that VALUE2 should be accessed in a static way. With javac -Xlint:all you will also get a warning. Other than this, SomeEnum.VALUE1.VALUE2 is exactly the same as SomeEnum.VALUE2. The enum constants are represented as static fields.

Answer 2

if (someObject.getStatus() == SomeEnum.VALUE1.VALUE2) { ... }

is equivalent to

if (someObject.getStatus() == SomeEnum.VALUE2) { ... }

== will compare the memory address on both sides for non-primitive types.