Using underscores in Java variables and method nam

Question

Even nowadays I often see underscores in Java variables and methods, an example are member variables (like "m_count" or "_count"). As far as I remember, to use underscores in these cases is called bad style by Sun.

The only place they should be used is in constants (like in "public final static int IS_OKAY = 1;"), because constants should be all upper case and not camel case. Here, the underscore should make the code more readable.

Do you think using underscores in Java is bad style? If so (or not), why?

Answer 1

• I happen to like leading underscores for (private) instance variables, it seems easier to read and distinguish.Of course this thing can get you into trouble with edge cases (e.g. public instance variables (not common, I know) - either way you name them you're arguably breaking your naming convention:
• private int _my_int; public int myInt;? _my_int? )

-as much as I like the _style of this and think it's readable I find it's arguably more trouble than it's worth, as it's uncommon and it's likely not to match anything else in the codebase you're using.

-automated code generation (e.g. eclipse's generate getters, setters) aren't likely to understand this so you'll have to fix it by hand or muck with eclipse enough to get it to recognize.

Ultimately, you're going against the rest of the (java) world's prefs and are likely to have some annoyances from that. And as previous posters have mentioned, consistency in the codebase trumps all of the above issues.

Answer 2

sunDoesNotRecommendUnderscoresBecauseJavaVariableAndFunctionNamesTendToBeLongEnoughAsItIs();

as_others_have_said_consistency_is_the_important_thing_here_so_chose_whatever_you_think_is_more_readable();

Answer 3

It's a blend of coding styles. One school of thought is to preface private members with an underscore to distinguish them.

setBar( int bar)
{
   _bar = bar;
}

instead of

setBar( int bar)
{
   this.bar = bar;
}

Others will use underscores to indicate a temp local variable that will go out of scope at the end of the method call. (I find this pretty useless - a good method shouldn't be that long, and the declaration is RIGHT THERE! so I know it goes out of scope) Edit: God forbid a programmer from this school and a programmer from the memberData school collaborate! It would be hell.

Sometimes, generated code will preface variables with _ or __. The idea being that no human would ever do this, so it's safe.

Answer 4

using 'm_' or '_' in the front of a variable makes it easier to spot member variables in methods throughout an object.

As a side benefit typing 'm_' or '_' will make intellsense pop them up first ;)

Answer 5

Rules:

1. Do what the code you are editing does
2. If #1 doesn't apply, use camelCase, no underscores

Answer 6

It's nice to have something to distinguish private vs. public variables, but I don't like '_' in general coding. If I can help it in new code, I avoid their use.