This is the number one programming error I've seen (not the only one though).
Most of the time it is controlling logic that never gets executed.
I'm always curious as to why it is never caught and what it will do when fixed.
The problem is other programming languages do compare this way. As well as
some expression languages.
IMO Java should treat "==" as "object.equals" on objects and introduce another
operator for object pointer comparison like ".="
I don't think we'll ever see it though because it affects a lot of existing
source code making it not backwards compatible.
Shawn D. Garner
> From: [EMAIL PROTECTED]
> To: user@commons.apache.org; [EMAIL PROTECTED]
> Date: Mon, 17 Dec 2007 04:32:44 -0500
> Subject: RE: [lang] equalsBuilder unexplained wrong equality with
> java.lang.Longs ?
>
> Hello Laurent:
>
> This behavior is 'normal'. The concepts of object equality (the equals()
> method) and object identity (==) are different. The method ' equals()'
> defined in Object can be overridden by subclasses and defines if an object is
> 'equal' to another. Long overrides the equals method to check to see if the
> object passed in wraps the same primitive long value. OTOH, the == operator
> compares two object identities, that is, is the object on the left-hand side
> the same object as the one on the right-hand side. Even though two objects
> instances may be semantically equal (as in the example below), they are not
> the same object so fails the == comparison.
>
> For example:
>
> public class TestLongEquals extends TestCase {
>
> public void testname() throws Exception {
> Long long1a = new Long(1);
> Long long1b = new Long(1);
> Assert.assertFalse(long1a == long1b);
> Assert.assertTrue(long1a.equals(long1b));
> }
> }
>
> Gary
> Seagull Software
>
> > -----Original Message-----
> > From: Laurent Perez [mailto:[EMAIL PROTECTED]
> > Sent: Sunday, December 16, 2007 3:17 PM
> > To: Jakarta Commons Users List
> > Subject: [lang] equalsBuilder unexplained wrong equality with
> > java.lang.Longs ?
> >
> > Hi !
> >
> > I'm struggling with a problem I don't understand, my equalsBuilder's
> > isEquals seem to return false when dealing with Longs :
> >
> > I have a bean class UiTheme, with a property private Long id.
> >
> > The following equals builder will return false when this.id = 1 and
> > rhs.id = 1 :
> >
> > public boolean equals(Object object) {
> > if (!(object instanceof UiTheme)) {
> > return false;
> > }
> > UiTheme rhs = (UiTheme) object;
> > return new
> > EqualsBuilder().appendSuper(super.equals(object)).append(this.id,
> > rhs.id).isEquals();
> > }
> >
> > If I manually do the equality, as in this.id.equals(rhs.id), then it
> > is true (because, well... 1 = 1 !)
> > If I do an equality like this.id == rhs.id, then it is false (being a
> > Java newbie... maybe it should be false, not sure if doing == instead
> > of equals(obj) is correct with Longs)
> >
> > So I assume (am I wrong ?) that equalsBuilder's isEquals uses "=="
> > instead of "equals(obj)"... but I really, really don't understand why.
> >
> > Can anyone enlighten me ?
> >
> > thanks !
> > --
> > <a href="http://in-pocket.blogspot.com";>http://in-pocket.blogspot.com
> > - Mobile world, technology and more</a>
> >
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