Why is ""+ int flagged for Java in SonarQube

Question

In Java I can convert an int to a string by "" + intValue. Sonarqube and sonarlint flag this as inappropriate.

Why is this inappropriate. As far as I know Integer.toString(intValue) is more verbose and does the same.

I can imagine to flag it if not "" but Object x is used as in x + intValue where x is initialized as an integer. Ran into something like that with Javascript code.

because that is the most incorrect, naive way of converting an int ( or any other Object ) to a String representation that you can pick. This has been discourage for over a decade at this point. — user177800
– user177800, Commented Jan 7, 2016 at 14:50
@JarrodRoberson question is not a duplicate of the one you linked ! — benzonico
– benzonico, Commented Jan 7, 2016 at 14:51
@Hans would you mind providing the rule key raising the issue? — benzonico
– benzonico, Commented Jan 7, 2016 at 14:51
This is the duplicate that I was trying to copy paste as the close reason. The accepted answer answers this as well. — user177800
– user177800, Commented Jan 7, 2016 at 14:54

samczsun · Accepted Answer · 2016-01-07 15:12:09Z

8

With regards to why it's bad, Java automatically optimizes String concatenation to use StringBuilder instead. This means that by doing this

"" + d

You're actually doing

new StringBuilder().append(d).toString();

And if you do

d + ""

You end up compiling

new StringBuilder(String.valueOf(d)).toString();

Which is a pretty big waste of resources relative to just calling

String.valueOf(d);

answered Jan 7, 2016 at 15:12

samczsun

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