Should StringBuilder.append() be always preferred than concatenation?

Question

I have some code like this:

StringBuilder rgba = new StringBuilder(); for (...){ .... rgba.append(value + ", "); }

IntelliJ shows me the following warning:

string concatenation as argument to 'stringbuilder.append()' call

From here, here and other sources I understand that concatenation is actually creates a new String object and that negates the whole point of using a StringBuilder.
So IntelliJsuggests me to use

rgba.append(value); rgba.append(", ");

instead of

rgba.append(value + ", ");

But will this really be better?
Will this code be clearer?
Will this make the execution faster?

frankly, for this particular scenario I wouldn't give a second thought about "what is better" (how better? by which metric?). Concerning clearer, I would say "agree with Intellij" here, as you already have a SB instance anyway, would look more concise to just write one more append call, rather than throw concatenation in the mix — 62mkv
– 62mkv, Commented Mar 8, 2021 at 11:51
actually Intellij provides the reasoning concerning performance as well: Reports String concatenation used as the argument to StringBuffer.append(), StringBuilder.append() or Appendable.append(). Such calls may profitably be turned into chained append calls on the existing StringBuffer/Builder/Appendable, saving the cost of an extra StringBuffer/Builder allocation. This inspection ignores compile time evaluated String concatenations, which when converted to chained append calls would only worsen performance. — 62mkv
– 62mkv, Commented Mar 8, 2021 at 11:54
The append code will be clearer to the humans that have to read your code months or years later, including yourself. — Gilbert Le Blanc
– Gilbert Le Blanc, Commented Mar 8, 2021 at 12:37

62mkv · Accepted Answer · 2021-03-08 11:55:38Z

as per IntelliJ reasoning:

Reports String concatenation used as the argument to StringBuffer.append(), StringBuilder.append() or Appendable.append(). Such calls may profitably be turned into chained append calls on the existing StringBuffer/Builder/Appendable, saving the cost of an extra StringBuffer/Builder allocation. This inspection ignores compile time evaluated String concatenations, which when converted to chained append calls would only worsen performance.

so, I would say: go for it!

Henry Twist · Accepted Answer · 2021-03-08 12:26:03Z

What you've said is correct in the sense that a mixture of concatenation and StringBuilder goes against the point of using it in theory, but the extra performance we're talking about is incredibly minimal unless you're loop has a massive number of iterations.

In terms of code clarity I think the double append is actually a lot clearer considering you're using it anyway.

I would see the two statements as

Append ", " appended on "value"

Append "value" Append ", "

of which the second actually seems more concise, even if the code is technically longer.

mflorczak · Accepted Answer · 2021-03-08 11:53:04Z

0

In my opinion concatenation is much more readable for developers but StringBuilder.append is performant

answered Mar 8, 2021 at 11:53

mflorczak

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1 Comment

user15244370 Over a year ago

rgba.append(value).append(", ") can also be considered as clear as rgba.append(value + ", ") (or even clearer IMHO, when I want to highlight appending the comma)

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