Re: Smuggling information to enums
Roedy Green wrote:
What the techniques are there for smuggling information to enums?
they don't have constructors. It is not clear how you would make
them nested classes.
enums are singletons, they do have constructors, but they are called
only once per classloader that loads them.
Is it possible to somehow have two enum class objects in RAM at once,
each with different instance data?
see above.
Do you have to pass it in each time with the method or use static
setters?
That is one approach. It is called the flyweight pattern. I wrote a blog
about it a while ago.
<http://virtualinfinity.net/wordpress/program-design/2007/10/22/using-enums-as-a-flyweight-pattern/>
Enums are full classes. They can have constructors, and they can have
instance data, and they can have methods.
public enum MyEnum {
A("Test"),
B('c', 42, "Chicken") {
public void blah() {
System.out.println("blurp");
}
}
;
public final String name;
public final char answer;
public final int answer2;
public final String taste;
MyEnum(String name) {
taste = "Water";
answer = 'a';
answer2 = -1;
this.name = name;
}
MyEnum(char theAnswerIsAlways, int theAnswerToEverything,
String tasteLike) {
name = "Answers";
taste = tasteLike;
answer = theAnswerIsAlways;
answer2 = theAnswerToEverything;
}
public void blah() {
System.out.println("Blah!");
}
}
public class Test {
public static void main(String...args) {
MyEnum val = MyEnum.A;
System.out.println(val.name);
System.out.println(val.answer);
System.out.println(val.answer2);
System.out.println(val.taste);
val.blah();
val = MyEnum.B;
System.out.println(val.name);
System.out.println(val.answer);
System.out.println(val.answer2);
System.out.println(val.taste);
val.blah();
}
}
Output:
Test
a
-1
Water
Blah!
Answers
c
42
Chicken
blurp
--
Daniel Pitts' Tech Blog: <http://virtualinfinity.net/wordpress/>