Using a char array in string concatenation

[Rahul Kakkar]

It is recommeded that we should not use a char array in string concatenation. For instance, "hello" + new char[]{'w','o','r','l','d'} is bad.

But why is this so?

[Ken Blair]

Because what you're doing is basically the equivalent of:

StringBuilder s = new StringBuilder();
s.append("Hello ");
s.append((Object)new char[] {'W', 'o', 'r', 'l', 'd'});
String newString = s.toString();

That will indirectly lead to it using the Object.toString() implementation for the char[] which gives you [C@hashcode instead of an equivalent String. I'm not sure why exactly the compiler doesn't use append(char[]) instead of append(Object) but I'm sure someone else will chime in with that.

[Rahul Kakkar]

okay got it, thanks. I just saw the bytecode and confirmed it. Should've have done that prior to posting here, but anyway.