Re: Distinct ID Number Per Object?

From:

ram@zedat.fu-berlin.de (Stefan Ram)

Newsgroups:

comp.lang.java.programmer

Date:

16 Jun 2007 20:51:11 GMT

Message-ID:

<identityHashCode-20070616224926@ram.dialup.fu-berlin.de>

Mark Thornton <mark.p.thornton@ntl-spam-world.com> writes:

While the objects address may be unique (amongst objects existing at a
given time), the value returned by System.identityHashCode is NOT
guaranteed to be unique. Indeed in some cases it couldn't be. The
hashCode is a 32 bit integer, but a 64 bit VM could have more than 2^32
objects, in which case some of those objects would have the same hash code.

  I am somewhat disappointed, that no one has yet
  reported about results from the program I posted in

<identityHashCode-20070616191650@ram.dialup.fu-berlin.de>

public class Main
{ final static java.lang.String lineSeparator =
  java.lang.System.getProperty( "line.separator" );
  public static void main( final java.lang.String[] args )
  { final java.lang.Object object = new java.lang.Object();
    final int code = object.hashCode();
    java.lang.Object object1;
    int code1;
    do
    { code1 =( object1 = new java.lang.Object() ).hashCode(); }
    while( code1 != code );
    java.lang.System.out.print
    (( object == object1 )+ lineSeparator +
      code + lineSeparator +
      code1 + lineSeparator ); }}