...
Also, the primary question is self-reported equality of File objects,
not String equality of their names. Are those always the same?
Good question. File equality can't be equivalent to equality of canonical
paths, since computing a canonical path can throw an IOException, and
computing equality can't.
The docs say:
Tests this abstract pathname for equality with the given object. Returns
true if and only if the argument is not null and is an abstract pathname
that denotes the same file or directory as this abstract pathname.
Whether or not two abstract pathnames are equal depends upon the
underlying system. On UNIX systems, alphabetic case is significant in
comparing pathnames; on Microsoft Windows systems it is not.
This specification is incoherent, given the existence of VFAT and HFS+ on
unix machines.
Furthermore, i strongly suspect that it's simply a lie. The beginning of
the description sounds like something that only getCanonicalPath could
implement, and i can't believe equals is using that. A small test:
import java.io.* ;
public class FileEquals {
public static void main(String[] args) throws IOException {
File a = new File(args[0]) ;
File b = new File(args[1]) ;
System.out.println("File.equals: " + a.equals(b)) ;
System.out.println("File.getCanonicalPath.equals: "
+ a.getCanonicalPath().equals(b.getCanonicalPath())) ;
}
}
Hooke:~/Temp tom$ uname -a
Darwin Hooke.local 8.11.0 Darwin Kernel Version 8.11.0: Wed Oct 10 18:26:00 PDT 2007; root:xnu-792.24.17~1/RELEASE_PPC Power Macintosh powerpc
Hooke:~/Temp tom$ java -version
java version "1.5.0_16"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_16-b06-275)
Java HotSpot(TM) Client VM (build 1.5.0_16-132, mixed mode, sharing)
Hooke:~/Temp tom$ java FileEquals FileEquals.java FileEquals.java
File.equals: true
File.getCanonicalPath.equals: true
Hooke:~/Temp tom$ java FileEquals FileEquals.java FileEquals.JAVA
File.equals: false
File.getCanonicalPath.equals: true
Hooke:~/Temp tom$ ln -s FileEquals.java FileEquals.link
Hooke:~/Temp tom$ java FileEquals FileEquals.java FileEquals.link
File.equals: false
File.getCanonicalPath.equals: true
According to the javadoc, all three of those should be equal.
tom
