Naming convention for boolean returning methods

Question

There's a convention for boolean property accessors to name them like isX().

Does it apply to all boolean returning methods that are not invoked for their useful side effects, like this one?

Also, should I replace "is" with "are" if the noun is plural?

"Follow you team's guidelines" is not applicable since we have none (but I wish to bring more sense into the codebase).

// inside JTable wrapper
 public boolean multipleRowsSelected() {
 int[] selectedRows = getSelectedRows();
 return selectedRows != null && selectedRows.length > 1;
 }

• JimmyJames: As a note on style, this kind or method seems unnecessarily granular. IMO it is sufficient to implement a rowSelectedCount method that returns int and converts null to 0.
• Filip Milovanović: '"Follow you team's guidelines" is not applicable since we have none' - well, then have a meeting and decide how you want to do it (possibly including in what cases it is OK to deviate from that decision). If you have retros, you could bring it up there. There's no industry consensus on this, different teams follow different conventions. A lot of it might come down to personal taste. E.g., one thing to consider is what reads better for you: if (areMultipleRowsSelected()) vs if (multipleRowsSelected()).
• Filip Milovanović: BTW, one of the answers made the distinction between question and predicate forms, and I'd like to point out multipleRowsSelected is just a shorter variant of the predicate form.
• k314159: You're using JTable, which has a boolean method called getAutoCreateRowSorter - so even the Java API doesn't adhere to its own naming guidelines.

Answer 1

The use of a verb (is, get) for a method goes hand in hand with the use of noun/adjective for a variable/field.

boolean selected = line.isSelected();
boolean lineSelected = line.isSelected();

Mind that this convention is not very tight in this field as opposed to word capitalization. For booleans one the possible formulations - when a noun is used:

• as predicate (noun-is-adjective) or

• as question (is-noun-adjective).

  boolean lineSelected = line.lineIsSelected();
  boolean lineSelected = line.isLineSelected(); // UGLY IMHO
  boolean multipleRowsSelected = table.multipleRowsAreSelected();
  boolean multipleRowsSelected = table.areMultipleRowsSelected(); // UGLY IMHO
  

Though the question form has a prefix systematic, always is/are in front. But a predicate is more operational correct.

With respect to using are. That really is acceptable, as many predicates have other verbs like have or contains.

Also one often can see the compound structure exposed; something like:

table.getSelectionMode().isMultiple()

Some other perspectives

Getters and setters are a bit tainted or at least called boiler plate code. Other styles exist. Argumently not much better is the latest style of the java record classes:

record Point(int x, int y) {};
Point pt = new Point(3, 4);
int x = pt.x();

And similar:

int x = obj.x(); // Getter.
obj.x(30); // Setter.

Here every categpry is generalized to a noun. A kind of Chinese.

Answer 2

IsX has become conventional and thus has some usability benefits. We see IsX and know it's a boolean flag.

But I would advise against trying to make your methods follow english grammar too closely.

For the same reason you avoid plurals, for every case where a choice makes you code grammatical, there is a case where it makes it ungrammatical or ugly.

obj.IsX = true; //ungrammatical
if(obj.IsX) //grammatical
people.add(person) //grammatical
foreach(person in people) //hmmmm
people.contains(person) //???!
personList.contains(person) //grammatical in more cases.

For your specific case of table.multipleRowsSelected It seems like it's already covered by table.getSelectedRows().length > 1, but if you really need it then yes I would switch to an IsSomething rather than table.AreMultipleRowsSelected.

Has is almost as popular as Is so..

table.HasMultipleRowsSelected

Or Maybe you could do a combination of

table.IsAnyRowSelected && ! table.IsSingleRowSelected

Or if you need to differentiate these tables in a general sense, you can choose a noun.

table.IsMultiplex

If you use this across the board you can talk about "multiplex tables" and everyone knows what you mean.

• Sergey Zolotarev: Thank you. So what is you advice for my specific case?
• Sergey Zolotarev: "I would switch to an IsSomething rather than table.AreMultipleRowsSelected" Do you mean I should avoid plural nouns in such cases?
• Sergey Zolotarev: But you do agree that isMultipleRowsSelected() is nonsense, don't you? We have a lot of methods like that. I understand you want to replace the plural noun
• Sergey Zolotarev: But it is so blatantly ungrammatical, in any context!!
• Ewan: I think this is the point of my answer. "IsX", "HasX" are in common usage and the meaning is well understood. Use this standard because of that. Not because sometimes its grammatical in english, and DEFINITELY don't go through refactoring standard following names to make you code read like english.

Answer 3

Obviously "is" is stupid if it’s not true. You may have prefixes like "has" (like a button is not a title, but a button can have a title). Or "can" (you can paste text into a text field but not an audio file), or other suffixes describing correctly what the result of the Boolean function is.

• Greg Burghardt: 'Obviously "is" is stupid if it’s not true." — how so?
• gnasher729: You have a button object. Buttons can have titles, or not have titles. They are not titles, So aButton.isTitle is nonsense and stupid. But why do I have to explain that?
• Giacomo Catenazzi: Because you want use isTitles but isTitled. It is not just "is" but the whole name that should be selected sanely. Apple name conventions document talks probably too much about grammars.
• Greg Burghardt: Ok, perhaps I misunderstood your statement. Are you saying that using "is" in a name that doesn't imply a yes/no answer is illogical? If that's what you meant, then I agree, but the statement might be overly broad to universally think "is" in a name should be forbidden.
• Greg Burghardt: I read your statement as "is" is stupid if it's (false) ... which threw me for a loop.