`val str = StringBuilder (); str.append("hello");`...

# kotlin-native

[Kavan]

val str = StringBuilder (); str.append("hello");

var str = ""; str += "hello";

Second is faster then first one.
Shouldn't take same time ? If not then.
When to use first and when to use second ?

[Sam]

str isn’t the same object type between your two examples.

val b = StringBuilder()
b.append("hello")
val str = b.toString()

Allocations are relatively cheap so for minor amounts of string concatenation, the code is often clearer with just str += "hello" but if you’re going to be doing heavy manipulation of the string before it is fully constructed a StringBuilder should perform better. Try a heavier example like this and see how it performs:

val b = StringBuilder()
repeat(1000) {
    b.append("Hello")
}
repeat(1000) {
    b.deleteCharAt(b.length / 2)
}
val str = b.toString()

[Kavan]

Got it. Thanks.

[Dico]

deleteCharAt probably doesn't have such great performance.

[Dico]

Probably better than concatenating 2 sub strings though

[Dico]

So good example