When using the Predicate interface, I thought it would be useful to be
able to negate a predicate rather than writing a new one with the
opposite behavior. Soon afterwards, I encountered a real need for
such a thing, so I wrote it. If you think this would be useful to add
to the library (as I do IMHO), feel free to do so, or let me know how
I can be of help in doing so. Here it is:
-----
import org.apache.commons.collections.Predicate;
/**
* Wraps a Predicate and reverses its return value.
*/
public class NegatingPredicate implements Predicate
{
private Predicate predicate;
/**
* Creates an instance with the specified Predicate.
*
* @param p the predicate to wrap and reverse
*/
NegatingPredicate(Predicate p) {
predicate = p;
}
/**
* Gets the result of the wrapped Predicate and negates it.
*
* @param o the object to evaluate
*/
public boolean evaluate(Object o) {
return ! predicate.evaluate(o);
}
}
-----
- Keith Bennett
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