Strings in Switch

[Ulf Zibis]

Yes, but ONLY if hash code is not calculated yet AND equals() is invoked 
1st time.
I assume, that all interned Strings e.g. constants yet have the hash 
value precalculated.
This is to avoid (1) the little more expensive hash code computation if 
a short living string is only equated once, and (2) an additional field 
in each string object to save a kind of threshold marker.
The win of adding hash code compare into String#equals() would come to 
account, if a string would be equated often.

-Ulf


Am 09.12.2009 19:05, Neal Gafter schrieb:
> Do you really want to set the has code of every string in the world to -1?
>
> On Wed, Dec 9, 2009 at 9:58 AM, Ulf Zibis <Ulf.Zibis at gmx.de 
> <mailto:Ulf.Zibis at gmx.de>> wrote:
>
>        public boolean equals(Object anObject) { ...
>
>                    if (hash == 0)
>                        hash = -1;        // mark 1st invokation of
>     equals()
>                    else if (anotherString.hash == 0)
>                        anotherString.hash == -1; // mark 1st invokation "
>        ... }
>
>        public int hashCode() {
>            int h = hash;
>            if (h == 0 || ++h == 0) { ...
>            }
>            return h;
>        }
>
>