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 java.util.concurrent.atomic.AtomicInteger;
20
21 import org.apache.commons.functor.BinaryPredicate;
22 import org.apache.commons.functor.NullaryPredicate;
23 import org.apache.commons.functor.Predicate;
24 import org.apache.commons.lang3.Validate;
25
26 /**
27 * A predicate that returns <code>false</code>
28 * the first <i>n</i> times it is invoked, and
29 * <code>true</code> thereafter.
30 *
31 * @since 1.0
32 * @version $Revision: 1539877 $ $Date: 2013-11-08 01:20:07 +0100 (Fr, 08 Nov 2013) $
33 */
34 public final class Offset implements NullaryPredicate, Predicate<Object>,
35 BinaryPredicate<Object, Object> {
36 // instance variables
37 //---------------------------------------------------------------
38 /**
39 * The number of times the predicate must return {@code false}.
40 */
41 private final int min;
42 /**
43 * The current number of times the predicate has been invoked.
44 */
45 private AtomicInteger state = new AtomicInteger();
46
47 /**
48 * Create a new Offset.
49 * @param count offset
50 */
51 public Offset(int count) {
52 Validate.isTrue(count >= 0, "Argument must be a non-negative integer.");
53 this.min = count;
54 }
55
56 /**
57 * {@inheritDoc}
58 */
59 public boolean test() {
60 // stop incrementing when we've hit max, so we don't loop around
61 if (state.get() < min) {
62 state.incrementAndGet();
63 return false;
64 }
65 return true;
66 }
67
68 /**
69 * {@inheritDoc}
70 */
71 public boolean test(Object obj) {
72 return test();
73 }
74
75 /**
76 * {@inheritDoc}
77 */
78 public boolean test(Object a, Object b) {
79 return test();
80 }
81
82 /**
83 * {@inheritDoc}
84 */
85 @Override
86 public boolean equals(Object obj) {
87 if (obj == this) {
88 return true;
89 }
90 if (!(obj instanceof Offset)) {
91 return false;
92 }
93 Offset other = (Offset) obj;
94 return other.min == min;
95 }
96
97 /**
98 * {@inheritDoc}
99 */
100 @Override
101 public int hashCode() {
102 int result = "Offset".hashCode();
103 result <<= 2;
104 result ^= min;
105 return result;
106 }
107
108 /**
109 * {@inheritDoc}
110 */
111 @Override
112 public String toString() {
113 return "Offset<" + min + ">";
114 }
115
116 //default == equals/hashCode due to statefulness
117 }