scala 2.10 - Stringbuilder constructor not working

Question

I came across this issue when I was trying to form strings build with Integers. I used scala's Stringbuilder and see this weird behavior.

println(new StringBuilder(1).append(2).append(3))
>23
println(new StringBuilder(1.toString()).append(2).append(3))
>123

Am I doing something wrong or just implicit conversion not taking place in constructor argument and ignores it silently.

Answer 1

The constructor takes an Int for starting capacity, which is why you don't see it as output in your string:

def this(capacity: Int) = this(capacity, "")

Answer 2

You are using 2 different constructors:

1. StringBuilder(int capacity): Constructs a string builder with no characters in it and an initial capacity specified by the capacity argument.
2. StringBuilder(String str): Constructs a string builder initialized to the contents of the specified string.

So new StringBuilder(1) returns an empty new StringBuilder of initial capacity 1.