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.algorithm;
18
19 import java.io.Serializable;
20
21 import org.apache.commons.functor.BinaryFunction;
22 import org.apache.commons.functor.UnaryPredicate;
23 import org.apache.commons.functor.UnaryProcedure;
24 import org.apache.commons.functor.generator.Generator;
25
26 /**
27 * Return the index of the first Object in a {@link Generator} matching a {@link UnaryPredicate}, or -1 if not found.
28 *
29 * @version $Revision: 1156337 $ $Date: 2011-08-10 21:44:54 +0200 (Wed, 10 Aug 2011) $
30 */
31 public final class IndexOfInGenerator<T>
32 implements BinaryFunction<Generator<? extends T>, UnaryPredicate<? super T>, Number>, Serializable {
33 /**
34 * serialVersionUID declaration.
35 */
36 private static final long serialVersionUID = -11365986575536471L;
37 private static final IndexOfInGenerator<Object> INSTANCE = new IndexOfInGenerator<Object>();
38
39 /**
40 * Helper procedure.
41 */
42 private static class IndexProcedure<T> implements UnaryProcedure<T> {
43 private final Generator<? extends T> generator;
44 private final UnaryPredicate<? super T> pred;
45 private long index = -1L;
46 private long current = 0L;
47
48 /**
49 * Create a new IndexProcedure.
50 * @pred test
51 */
52 IndexProcedure(Generator<? extends T> generator, UnaryPredicate<? super T> pred) {
53 this.generator = generator;
54 this.pred = pred;
55 }
56
57 /**
58 * {@inheritDoc}
59 */
60 public void run(T obj) {
61 if (index < 0 && pred.test(obj)) {
62 index = current;
63 generator.stop();
64 }
65 current++;
66 }
67 }
68
69 /**
70 * {@inheritDoc}
71 * @param left Generator
72 * @param right UnaryPredicate
73 */
74 public Number evaluate(Generator<? extends T> left, UnaryPredicate<? super T> right) {
75 IndexProcedure<T> findProcedure = new IndexProcedure<T>(left, right);
76 left.run(findProcedure);
77 return findProcedure.index;
78 }
79
80 /**
81 * {@inheritDoc}
82 */
83 public boolean equals(Object obj) {
84 return obj == this || obj != null && obj.getClass().equals(getClass());
85 }
86
87 /**
88 * {@inheritDoc}
89 */
90 public int hashCode() {
91 return System.identityHashCode(INSTANCE);
92 }
93
94 /**
95 * Get a static {@link IndexOfInGenerator} instance.
96 * @return {@link IndexOfInGenerator}
97 */
98 public static IndexOfInGenerator<Object> instance() {
99 return INSTANCE;
100 }
101 }