com.samskivert.util

Class Predicate<T>

java.lang.Object

com.samskivert.util.Predicate<T>

Direct Known Subclasses:

Predicate.And, Predicate.InstanceOf, Predicate.Not, Predicate.Or

@ReplacedBy(value="com.google.common.base.Predicate")
public abstract class Predicate<T>
extends Object

Arbitrates membership. Example usage. Find the best kind of peanut butter:

 public Iterator<PeanutButter> findBestKinds (Collection<PeanutButter> pbs)
 {
     return new Predicate<PeanutButter>() {
         public boolean isMatch (PeanutButter pb)
         {
              return pb.isCreamy() && !pb.containsPartiallyHydrogenatedOils();
         }
     }.filter(pbs.iterator());
 }
 

An interface like this may someday be in the Java library, but until then...

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Predicate.And<T> Includes an object if and only if all the predicates with which it was constructed also include the object.
static class	Predicate.InstanceOf<T> A simple predicate that includes an object if it is an instance of the specified class.
static class	Predicate.Not<T> Negates any other predicate.
static class	Predicate.Or<T> Includes an object if at least one of the predicates specified in the constructor include the object.

Constructor Summary

Constructors

Constructor and Description
Predicate()

Method Summary

Modifier and Type	Method and Description
<E extends T> Collection<E>	createView(Collection<E> input) Create a view of the specified collection that only contains elements that match the predicate.
<E extends T> Iterable<E>	createView(Iterable<E> input) Create an Iterable view of the specified Iterable that only contains elements that match the predicate.
static <T> Predicate<T>	falseInstance() Returns a type-safe reference to the shared instance of a predicate that always returns false.
<E extends T> void	filter(Collection<E> coll) Remove non-matching elements from the specified collection.
<E extends T> Iterator<E>	filter(Iterator<E> input) Return a new iterator that contains only matching elements from the input iterator.
abstract boolean	isMatch(T obj) Does the specified object belong to the special set that we test for?
static <T> Predicate<T>	trueInstance() Returns a type-safe reference to the shared instance of a predicate that always returns true.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Predicate

public Predicate()

Method Detail

trueInstance

public static <T> Predicate<T> trueInstance()

Returns a type-safe reference to the shared instance of a predicate that always returns true.

falseInstance

public static <T> Predicate<T> falseInstance()

Returns a type-safe reference to the shared instance of a predicate that always returns false.

isMatch

public abstract boolean isMatch(T obj)

Does the specified object belong to the special set that we test for?

filter

public <E extends T> Iterator<E> filter(Iterator<E> input)

Return a new iterator that contains only matching elements from the input iterator.

filter

public <E extends T> void filter(Collection<E> coll)

Remove non-matching elements from the specified collection.

createView

public <E extends T> Iterable<E> createView(Iterable<E> input)

Create an Iterable view of the specified Iterable that only contains elements that match the predicate. This Iterable can be iterated over at any time in the future to view the current predicate-matching elements of the input Iterable.

createView

public <E extends T> Collection<E> createView(Collection<E> input)

Create a view of the specified collection that only contains elements that match the predicate. This collection can be examined at any time in the future to view the current predicate-matching elements of the input collection. Note that the view is not modifiable and currently has poor implementations of some methods.