Sorry, you were right there is no problem overflowing an int. Wish I
would have known that when writing some other hashCode methods. Thanks
for adding the braces.
john mcnally
Age Mooy wrote:
>
> Hmmm... I looked at the implementations of Hashtable and AbstractSet and both of
>them use this int addition
> scheme. I'm a little rusty on what happens when the number gets too big for an int
>but I did get some negative
> numbers in my tests. I could cast the whole lot to longs ?
> The only other method I've found while browsing through jdk source code is the
>bitwise XOR operator... would
> that be sufficient ? Do you have another suggestion ?
>
> The patch for that last one (incl. fancy brackets) would be:
>
> Index: src/java/org/apache/turbine/util/db/Criteria.java
> ===================================================================
> RCS file:
>/home/cvspublic/jakarta-turbine-2/src/java/org/apache/turbine/util/db/Criteria.java,v
> retrieving revision 1.1.1.1
> diff -u -r1.1.1.1 Criteria.java
> --- src/java/org/apache/turbine/util/db/Criteria.java 2001/08/16 05:09:46
>1.1.1.1
> +++ src/java/org/apache/turbine/util/db/Criteria.java 2001/09/27 22:29:07
> @@ -3650,6 +3650,36 @@
> return isEquiv;
> }
>
> + /**
> + * Returns a hash code value for the object.
> + */
> + public int hashCode()
> + {
> + int h = value.hashCode() ^ comparison.hashCode();
> +
> + if (table != null)
> + {
> + h ^= table.hashCode();
> + }
> +
> + if (column != null)
> + {
> + h ^= column.hashCode();
> + }
> +
> + if (and != null)
> + {
> + h ^= and.hashCode();
> + }
> +
> + if (or != null)
> + {
> + h ^= or.hashCode();
> + }
> +
> + return h;
> + }
> +
> public String[] getAllTables()
> {
> StringStackBuffer tables = new StringStackBuffer();
>
> Age
>
> > I think you need to be more careful of overflows.
> >
> > john mcnally
> >
> > Age Mooy wrote:
> > >
> > > Hi,
> > >
> > > I was trying to store query results in the global cache service using a key
>based on the hashcode of the
> > > Criteria object and I found out that hashcodes for equal Criteria are not equal.
>This breaks the
> > rules because
> > > the Java spec says something like this:
> > >
> > > "If two objects are equal according to the equals(Object) method, then calling
>the hashCode
> > method on each of
> > > the two objects must produce the same integer result"
> > >
> > > This problem occurs because the Criteria.Criterion inner class defines an
>equals() method without
> > defining a
> > > matching hashCode() method.
> > >
> > > I played around a bit and came up with this implementation:
> > >
> > > /**
> > > * Returns a hash code value for the object.
> > > */
> > > public int hashCode()
> > > {
> > > int h = value.hashCode() + comparison.hashCode();
> > >
> > > if (table != null)
> > > h += table.hashCode();
> > >
> > > if (column != null)
> > > h += column.hashCode();
> > >
> > > if (and != null)
> > > h += and.hashCode();
> > >
> > > if (or != null)
> > > h += or.hashCode();
> > >
> > > return h;
> > > }
> > >
> > > I'm no hashCode expert but it works consistently with my tests.
> > >
> > > The patch for the above code (in jakarta-turbine-2) is attached below,
> > > Age
> > >
> > > Index: src/java/org/apache/turbine/util/db/Criteria.java
> > > ===================================================================
> > > RCS file:
>/home/cvspublic/jakarta-turbine-2/src/java/org/apache/turbine/util/db/Criteria.java,v
> > > retrieving revision 1.1.1.1
> > > diff -u -r1.1.1.1 Criteria.java
> > > --- src/java/org/apache/turbine/util/db/Criteria.java 2001/08/16 05:09:46
>1.1.1.1
> > > +++ src/java/org/apache/turbine/util/db/Criteria.java 2001/09/27 14:11:14
> > > @@ -3650,6 +3650,28 @@
> > > return isEquiv;
> > > }
> > >
> > > + /**
> > > + * Returns a hash code value for the object.
> > > + */
> > > + public int hashCode()
> > > + {
> > > + int h = value.hashCode() + comparison.hashCode();
> > > +
> > > + if (table != null)
> > > + h += table.hashCode();
> > > +
> > > + if (column != null)
> > > + h += column.hashCode();
> > > +
> > > + if (and != null)
> > > + h += and.hashCode();
> > > +
> > > + if (or != null)
> > > + h += or.hashCode();
> > > +
> > > + return h;
> > > + }
> > > +
> > > public String[] getAllTables()
> > > {
> > > StringStackBuffer tables = new StringStackBuffer();
> > >
> > > ---------------------------------------------------------------------
> > > To unsubscribe, e-mail: [EMAIL PROTECTED]
> > > For additional commands, e-mail: [EMAIL PROTECTED]
> >
> > ---------------------------------------------------------------------
> > To unsubscribe, e-mail: [EMAIL PROTECTED]
> > For additional commands, e-mail: [EMAIL PROTECTED]
> >
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: [EMAIL PROTECTED]
> For additional commands, e-mail: [EMAIL PROTECTED]
---------------------------------------------------------------------
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
