Prior to Java 1.5 does not have enumerated types the way Pascal and C++ do.
With 1.5 there are now enums.
There are three ways to get around the problem:
- Create a Vegetable class just to hold your collection of public static final int
constants that encode the possibilities. In simple cases you don’t bother
with a separate Vegetable class for your constants. You just define them in the
JuiceBar class. The disadvantages of this method are:
- You just close your eyes to parameter type checking. To the compiler any int
will do as a parameter to a method expecting a Vegetable code. It does not care
if you pass a Vegetable code, or diameter in millimeters
- You have to manually assign numbers to each option.
- Create a Vegetable class to contain your collection of various named static
final objects to represent each possibility. The main problems with this
method are:
- Extra run time overhead.
- You have to create a separate Vegetable class. You can’t just piggyback
the constants inside the JuiceBar class that uses them.
- You can’t use your possibility constants in a switch statement. You need
to code with nested ifs and ==.
- It is difficult to store data externally, especially if you add or delete
possibilities and need to update existing databases.
- Similar to the second approach, but this time we arrange to make the
enumerations Serializable. The advantage are it is type safe and Serializable.
The main problems with this method are:
- Extra run time overhead.
- You have to create a separate Vegetable class. You can’t just piggyback
the constants inside the JuiceBar class that uses them.
- You can’t use your possibility constants in a switch statement. You need
to code with nested ifs and ==.
- You need to write a lot of code to convert back and forth between int and Object
form.
JavaWorld Magazine did an article
on various ways to kludge enumerations in Java. Philip Bishop did an article
on a type-safe scheme for both C++ and Java. John D. Mitchel did an article
on a scheme using the C preprocessor.
I wrote a proposal to properly build in two types of enumerations into the Java
glossary. I doubt we will ever have decent enumerations. The theoreticians seem
to think the coming genericity features of Java will be sufficient. Arrgh! They
don’t care how verbose the code is.
Perhaps what we could do in the interim is use a combined approach with even
more bells and whistles including a set of static final ints you can use as case
labels. You also need some external representations for use in an external
database, often a single character or a short string. These representations are
more immune to breaking your database when you add a new enum element. You use
an amanuensis to stomp out the repetitive code with a cookie cutter. You enter
svelte Pascal and out pops Divine Java.