CODEWITHSUNDEEP
javaeclipse
anon
anon

Reputation:

Best practice: How to handle type safety warnings?

The following statement causes a warning in Eclipse:

Map<String, String> options = DefaultCodeFormatterConstants.getEclipseDefaultSettings();

Warning:

Type safety: The expression of type Map needs unchecked conversion to conform to Map<String,String>

What is the best practice to handle this warning? Should I add an SupressWarning("unchecked") annotation? For the whole class? Or just the method? Or should I just ignore the warning? Or how can I get rid of this warning?

Upvotes: 2

Views: 3135

Answers (4)

JB Nizet
JB Nizet

Reputation: 691913

If the method returns a raw map, the only thing you can do is to make sure (from the doc or from the code) that the Map is indeed a Map<String, String>, and ignore the warning. The compiler doesn't have any way to check that the returned Map is ideed a Map<String, String>.

You should ignore the warning at the smallest possible scope, else other unsafe code could be added without warning from the compiler.

Upvotes: 1

user949300
user949300

Reputation: 15729

I find these warnings on the declaration line highly annoying. And meaningless, since, deep down inside, I know that there is type erasure and it the compiler is complaining about nothing. So I ignore them. However, this may not be a best practice and I'm quite interested in how others approach them. Java 7 made some improvements, IIRC, you can now go 

List<String> = new ArrayList<>();

and save some redundant typing of "String" and avoid the warning.

Note - I do pay attention to warnings that are not on the declaration line.

Upvotes: 1

Affe
Affe

Reputation: 47994

The only way to 'get rid' of it permanently is to upgrade to a Java 5 or later-only version of your API that returns a parameterized map.

The simplest thing to do to sort of 'clean it up' is wrap the method that returns a RAW type in a class of your own, perform the cast there, and suppress the unchecked warning. This way at least it's done in a single place and you're not using @SuppressWarnings all over the place where it may accidentally also hide a "genuine" warning.

Upvotes: 2

Laurence Gonsalves
Laurence Gonsalves

Reputation: 143264

Until DefaultCodeFormatterConstants.getEclipseDefaultSettings is properly generified, I'd consider making a generified wrapper for it, and having the annotation on the internal local variable declaration inside of it. Also include a comment explaining why the annotation is "safe".

In general, you want the scope of a SuppressWarnings annotation to be as small as possible, and you want to have as few of them as possible. You should also have a comment explaining your reasoning each time you use one.

Upvotes: 9

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