001 /*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017 package org.apache.commons.functor.core;
018
019 import org.apache.commons.functor.BinaryPredicate;
020 import org.apache.commons.functor.Predicate;
021 import org.apache.commons.functor.UnaryPredicate;
022
023 /**
024 * A predicate that returns <code>false</code>
025 * the first <i>n</i> times it is invoked, and
026 * <code>true</code> thereafter.
027 *
028 * @since 1.0
029 * @version $Revision: 1160413 $ $Date: 2011-08-22 22:12:28 +0200 (Mon, 22 Aug 2011) $
030 * @author Jason Horman (jason@jhorman.org)
031 * @author Rodney Waldhoff
032 */
033
034 public final class Offset implements Predicate, UnaryPredicate<Object>, BinaryPredicate<Object, Object> {
035 // instance variables
036 //---------------------------------------------------------------
037 /**
038 * The number of times the predicate must return {@code false}.
039 */
040 private final int min;
041 /**
042 * The current number of times the predicate has been invoked.
043 */
044 private int current;
045
046 /**
047 * Create a new Offset.
048 * @param count offset
049 */
050 public Offset(int count) {
051 if (count < 0) {
052 throw new IllegalArgumentException("Argument must be a non-negative integer.");
053 }
054 this.min = count;
055 }
056
057 /**
058 * {@inheritDoc}
059 */
060 public synchronized boolean test() {
061 // stop incrementing when we've hit max, so we don't loop around
062 if (current < min) {
063 current++;
064 return false;
065 }
066 return true;
067 }
068
069 /**
070 * {@inheritDoc}
071 */
072 public boolean test(Object obj) {
073 return test();
074 }
075
076 /**
077 * {@inheritDoc}
078 */
079 public boolean test(Object a, Object b) {
080 return test();
081 }
082
083 /**
084 * {@inheritDoc}
085 */
086 public String toString() {
087 return "Offset<" + min + ">";
088 }
089
090 //default == equals/hashCode due to statefulness
091 }