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From: roman on 20 Apr 2008 10:37

---

Hi guys,
I was modeling some kind of States domain, but I came up with two
solutions and I want to check with you this approaches.

The problem (very simple):
Theres a fixed set of States (no more than 7). Every state has a
description and some of them could be final.

Approach 1:
public enum State {
STATE1("State1", false),
STATE2("State2", false),
STATE3("State3", true),
STATE4("State4", false),
STATE5("State5", true);

private String description;
private boolean isFinal;

private State(String description, boolean isFinal) {
this.description = description;
this.isFinal = isFinal;
}

public boolean isFinal() {
return isFinal;
}
}

Approach 2:
public enum State {
STATE1("State1", false),
STATE2("State2", false),
STATE3("State3")
{ public boolean isFinal() {
return true;
}
},
STATE4("State4", false),
STATE5("State5")
{ public boolean isFinal() {
return true;
}
};

private String description;

private State(String description) {
this.description = description;
}

public boolean isFinal() {
return false;
}
}


I want to know your opinions about this two approaches (eg what is the
intent of each approach, what is it modeling, is there a third
approach that you think is better than the previous two?, etc)

Bye.

From: Daniel Pitts on 20 Apr 2008 13:56

---

roman wrote:
> Hi guys,
> I was modeling some kind of States domain, but I came up with two
> solutions and I want to check with you this approaches.
>
> The problem (very simple):
> Theres a fixed set of States (no more than 7). Every state has a
> description and some of them could be final.
>
> Approach 1:
> public enum State {
> STATE1("State1", false),
> STATE2("State2", false),
> STATE3("State3", true),
> STATE4("State4", false),
> STATE5("State5", true);
>
> private String description;
> private boolean isFinal;
>
> private State(String description, boolean isFinal) {
> this.description = description;
> this.isFinal = isFinal;
> }
>
> public boolean isFinal() {
> return isFinal;
> }
> }
>
> Approach 2:
> public enum State {
> STATE1("State1", false),
> STATE2("State2", false),
> STATE3("State3")
> { public boolean isFinal() {
> return true;
> }
> },
> STATE4("State4", false),
> STATE5("State5")
> { public boolean isFinal() {
> return true;
> }
> };
>
> private String description;
>
> private State(String description) {
> this.description = description;
> }
>
> public boolean isFinal() {
> return false;
> }
> }
>
>
> I want to know your opinions about this two approaches (eg what is the
> intent of each approach, what is it modeling, is there a third
> approach that you think is better than the previous two?, etc)
>
> Bye.
>

For your *exact* example, I would use a variation on the first one:

public enum State {
STATE1("State1"),
STATE2("State2"),
STATE3("State3", true),
STATE4("State4"),
STATE5("State5", true);

private final String description;
private final boolean isFinal;

private State(String description) {
this(description, false);
}

private State(String description, boolean isFinal) {
this.description = description;
this.isFinal = isFinal;
}

public boolean isFinal() {
return isFinal;
}
}

For more complicated examples, I may choose some combination. For
states that have multiple transitions, I might have a method that is
overridden by each. Any more complicated, and I'd probably abandon the
enum pattern and move on to full classes implementing a State interface
and/or extending an AbstractState base class.

--
Daniel Pitts' Tech Blog: <http://virtualinfinity.net/wordpress/>

From: roman on 20 Apr 2008 14:25

---

Fe de errata.

In Approach 2:
STATEX("StateX", false) would be STATEX("StateX"),

Sorry.



On Apr 20, 12:37 pm, roman <mario.ro...(a)gmail.com> wrote:
> Hi guys,
> I was modeling some kind of States domain, but I came up with two
> solutions and I want to check with you this approaches.
>
> The problem (very simple):
> Theres a fixed set of States (no more than 7). Every state has a
> description and some of them could be final.
>
> Approach 1:
> public enum State {
> STATE1("State1", false),
> STATE2("State2", false),
> STATE3("State3", true),
> STATE4("State4", false),
> STATE5("State5", true);
>
> private String description;
> private boolean isFinal;
>
> private State(String description, boolean isFinal) {
> this.description = description;
> this.isFinal = isFinal;
> }
>
> public boolean isFinal() {
> return isFinal;
> }
>
> }
>
> Approach 2:
> public enum State {
> STATE1("State1", false),
> STATE2("State2", false),
> STATE3("State3")
> { public boolean isFinal() {
> return true;
> }
> },
> STATE4("State4", false),
> STATE5("State5")
> { public boolean isFinal() {
> return true;
> }
> };
>
> private String description;
>
> private State(String description) {
> this.description = description;
> }
>
> public boolean isFinal() {
> return false;
> }
>
> }
>
> I want to know your opinions about this two approaches (eg what is the
> intent of each approach, what is it modeling, is there a third
> approach that you think is better than the previous two?, etc)
>
> Bye.

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