- /*
- * Copyright 2001-2004 The Apache Software Foundation
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
- package org.apache.commons.collections.functors;
-
- import java.io.Serializable;
- import java.util.HashSet;
- import java.util.Set;
-
- import org.apache.commons.collections.Predicate;
-
- /**
- * Predicate implementation that returns true the first time an object is
- * passed into the predicate.
- *
- * @since Commons Collections 3.0
- * @version $Revision: 1.4 $ $Date: 2004/05/16 11:16:01 $
- *
- * @author Stephen Colebourne
- */
- public final class UniquePredicate implements Predicate, Serializable {
-
- /** Serial version UID */
- static final long serialVersionUID = -3319417438027438040L;
-
- /** The set of previously seen objects */
- private final Set iSet = new HashSet();
-
- /**
- * Factory to create the predicate.
- *
- * @return the predicate
- * @throws IllegalArgumentException if the predicate is null
- */
- public static Predicate getInstance() {
- return new UniquePredicate();
- }
-
- /**
- * Constructor that performs no validation.
- * Use <code>getInstance</code> if you want that.
- */
- public UniquePredicate() {
- super();
- }
-
- /**
- * Evaluates the predicate returning true if the input object hasn't been
- * received yet.
- *
- * @param object the input object
- * @return true if this is the first time the object is seen
- */
- public boolean evaluate(Object object) {
- return iSet.add(object);
- }
-
- }