Coding Conventions - Naming Enums

This will probably not make me a lot of new friends, but it should be added that the C# people have a different guideline: The enum instances are "Pascal case" (upper/lower case mixed). See stackoverflow discussion and MSDN Enumeration Type Naming Guidelines.

As we are exchanging data with a C# system, I am tempted to copy their enums exactly, ignoring Java's "constants have uppercase names" convention. Thinking about it, I don't see much value in being restricted to uppercase for enum instances. For some purposes .name() is a handy shortcut to get a readable representation of an enum constant and a mixed case name would look nicer.

So, yes, I dare question the value of the Java enum naming convention. The fact that "the other half of the programming world" does indeed use a different style makes me think it is legitimate to doubt our own religion.

In our codebase; we typically declare enums in the class that they belong to.

So for your Fruit example, We would have a Fruit class, and inside that an Enum called Fruits.

Referencing it in the code looks like this: Fruit.Fruits.Apple, Fruit.Fruits.Pear, etc.

Constants follow along the same line, where they either get defined in the class to which they're relevant (so something like Fruit.ORANGE_BUSHEL_SIZE); or if they apply system-wide (i.e. an equivalent "null value" for ints) in a class named "ConstantManager" (or equivalent; like ConstantManager.NULL_INT). (side note; all our constants are in upper case)

As always, your coding standards probably differ from mine; so YMMV.

As already stated, enum instances should be uppercase according to the docs on the Oracle website (http://docs.oracle.com/javase/tutorial/java/javaOO/enum.html).

However, while looking through a JavaEE7 tutorial on the Oracle website (http://www.oracle.com/technetwork/java/javaee/downloads/index.html), I stumbled across the "Duke's bookstore" tutorial and in a class (tutorial\examples\case-studies\dukes-bookstore\src\main\java\javaeetutorial\dukesbookstore\components\AreaComponent.java), I found the following enum definition:

private enum PropertyKeys {
    alt, coords, shape, targetImage;
}

According to the conventions, it should have looked like:

public enum PropertyKeys {
    ALT("alt"), COORDS("coords"), SHAPE("shape"), TARGET_IMAGE("targetImage");

    private final String val;

    private PropertyKeys(String val) {
        this.val = val;
    }

    @Override
    public String toString() {
        return val;
    }
}

So it seems even the guys at Oracle sometimes trade convention with convenience.

Enums are classes and should follow the conventions for classes. Instances of an enum are constants and should follow the conventions for constants. So

enum Fruit {APPLE, ORANGE, BANANA, PEAR};

There is no reason for writing FruitEnum any more than FruitClass. You are just wasting four (or five) characters that add no information.

This approach is recommended by and used in the The Java™ Tutorial's examples themselves.