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kotlinlang

Is there any performance difference between `"${var1}${var2}"` and `var1 + var2` for string construction?

Right, I was just wondering which I should prefer when my values are known to be non-null strings.

In Ruby the template substitution is faster than string append.

I believe the first is compiled to a `StringBuilder` under-the-hood. I’m not sure about the second, if it goes to a StringBuilder or does normal String concatenation. But it should either be the same performance-wise or slightly faster

Sounds like templates are probably the way to go then.

I guess that best thing to do is to open kotlin bytecode, maybe decompile that to Java and see for yourself

I don't know when it was added. Javac will turn `+` operations into StringBuilder in 8+ at least. Not sure if it does it in 6 or 7. So could depend on which version of JDK, and could depend on whether Kotlin compiler is turning it into `+`, or turning it into StringBuilder?

in terms of which to prefer i would prefer string templates, it’s a feature of the language which makes life easier than having to do string concatenation in another way

i can’t imagine the performance difference (if there are any) would be significant enough to do things the _old way_

If I remember correctly, the resulting byte code is the same.

Capture.PNG

yup, it's the same (with `StringBuilder`)