Re: do I need to override the equals() method?
Mike Schilling wrote:
Lew wrote:
NetBeans has this feature also. Alt-Insert, "equals() and
hashCode()", checkbox the desired fields, shows side by side the
checkboxes for each method so you can do what Mike likes.
For a class 'Foonteger' with a single 'BigInteger' field 'value'
(checkbox checked) it inserted:
--------------------------------
@Override
public boolean equals( Object obj )
{
if ( obj == null )
{
return false;
}
if ( getClass() != obj.getClass() )
{
return false;
}
final Foonteger other = (Foonteger) obj;
if ( this.value != other.value &&
(this.value == null || !this.value.equals(
other.value )) ) {
return false;
}
return true;
}
@Override
public int hashCode()
{
int hash = 7;
return hash;
}
--------------------------------
Not my favorite implementation, but sufficient.
The hash is always 7? Yes, that doesn't break anything, but ...
Yeah, that bothers me, too.
IntelliJ (4.5, which is a bit long in the tooth) gives
public boolean equals(Object o)
{
if (this == o) return true;
if (!(o instanceof Foonteger)) return false;
final Foonteger foonteger = (Foonteger) o;
if (value != null ? !value.equals(foonteger.value) :
foonteger.value != null) return false;
return true;
}
public int hashCode()
{
return (value != null ? value.hashCode() : 0);
}
That is, IntelliJ gives a far better hash function, and the two
disagree about equals() appplied tio subclasses.
The trouble with applying 'equals()' to subclasses is that it breaks symmetry.
--
Lew
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