Re: noob question: string comparing

David Segall wrote On 07/31/06 12:20,:


    Sleight of hand, prestidigitation, trickery and ruses,
scams and frauds -- if I can grab other peoples' wallets,
it's all worth while! ;-)


    I'm not at all sure what you mean by a "default" property.
The String.equals() method makes a computation, just as other
equals() methods -- other anything() methods -- make their
computations. String.equals() takes one set of things into
account; BigInteger.equals() computes things differently;
neither seems (to me) to "default" to anything.


    Here I must disagree, although it's risky: I've used only
a couple dozen programming languages, well short of "most."
But among those I've used that support the notion of "reference"
as a first-class value, I cannot think of any that make Java
seem at all unusual in this regard. All of them made a clear
distinction between the reference and the thing referred to.

    In C, consider

    char *p = "Hello, world!";
    char *q = malloc(strlen(p) + 1); /* assume success */
    strcpy (q, p);

This fragment points p at a character string, then points q
at an exact copy of that string. At this point p and q are
not == because they point to different string instances, yet
strcmp(p, q) reports that the strings compare equal. This
should seem eerily similar to Java's behavior with

    String p = "Hello, world!";
    String q = new String(p);

    And if you find two notions of "equality" confusing, it's
a good thing you never encountered Lisp! My Lisp days are far
behind me and my memory of them has gone a bit foggy, but I
recall that Common Lisp supports at least four different notions
of equality, maybe five.


    I don't think the conclusion follows from the premise.

--
Eric.Sosman@sun.com