import ._ or import.{ classOne, classTwo}

Question

will chossing what classes I want from package will speed up compiling process ? If for example in package me.test I have 50 classess, and I just need two of them and I will do :

 import me.test.{ classOne, classTwo}

instead of

 import me.test._

? Thanks

Removing `[java]` as you don't appear to want the answer about Java. — Peter Lawrey, Oct 14 '13 at 11:14
possible duplicate of [Is wildcard import bad in Scala with respect to incremental compilation?](http://stackoverflow.com/questions/11291772/is-wildcard-import-bad-in-scala-with-respect-to-incremental-compilation) — om-nom-nom, Oct 14 '13 at 11:17

score 9 · Answer 1 · edited Oct 14 '13 at 11:31

While the performance impact is negligible, here are a few things that happen:

Code size grows, number of classes in a package will grow.
You won't know where Foo comes from. This if very often a problem. Eclipse is slow with really large projects.
Open declaration is only available for files fetched in the EclipseKeys.withSource phase of the SBT plugin. A lot of libraries DON'T have it.

A few things from the Twitter Scala Style Guideline that have come very handy in practice:

Sort imports alphabetically, they are a lot easier to follow visually.
Only use a wildcard import pkg._ for more than 6 classes imported.
Use the import pck.{ Class1, Obj1 } layout for up to 6 classes.
Use multi-row imports for clarity

score 1 · Answer 2 · answered Oct 14 '13 at 11:14

I don't think that it will make a significant difference for compilation speed.

In my opinion you should base that decision on what you want to communicate with that import.

Do you want to use the whole package? Use import me.test._.
Do you want to cherry-pick only some parts of the package? Use import me.test.{ ClassOne, classTwo }.

import ._ or import.{ classOne, classTwo}

2 Answers2