1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.functor.core;
18
19 import org.apache.commons.functor.BinaryPredicate;
20 import org.apache.commons.functor.Predicate;
21 import org.apache.commons.functor.UnaryPredicate;
22
23 /**
24 * A predicate that returns <code>false</code>
25 * the first <i>n</i> times it is invoked, and
26 * <code>true</code> thereafter.
27 *
28 * @since 1.0
29 * @version $Revision: 1160413 $ $Date: 2011-08-22 22:12:28 +0200 (Mon, 22 Aug 2011) $
30 * @author Jason Horman (jason@jhorman.org)
31 * @author Rodney Waldhoff
32 */
33
34 public final class Offset implements Predicate, UnaryPredicate<Object>, BinaryPredicate<Object, Object> {
35 // instance variables
36 //---------------------------------------------------------------
37 /**
38 * The number of times the predicate must return {@code false}.
39 */
40 private final int min;
41 /**
42 * The current number of times the predicate has been invoked.
43 */
44 private int current;
45
46 /**
47 * Create a new Offset.
48 * @param count offset
49 */
50 public Offset(int count) {
51 if (count < 0) {
52 throw new IllegalArgumentException("Argument must be a non-negative integer.");
53 }
54 this.min = count;
55 }
56
57 /**
58 * {@inheritDoc}
59 */
60 public synchronized boolean test() {
61 // stop incrementing when we've hit max, so we don't loop around
62 if (current < min) {
63 current++;
64 return false;
65 }
66 return true;
67 }
68
69 /**
70 * {@inheritDoc}
71 */
72 public boolean test(Object obj) {
73 return test();
74 }
75
76 /**
77 * {@inheritDoc}
78 */
79 public boolean test(Object a, Object b) {
80 return test();
81 }
82
83 /**
84 * {@inheritDoc}
85 */
86 public String toString() {
87 return "Offset<" + min + ">";
88 }
89
90 //default == equals/hashCode due to statefulness
91 }