001 /*
002 * Java Genetic Algorithm Library (jenetics-1.6.0).
003 * Copyright (c) 2007-2014 Franz Wilhelmstötter
004 *
005 * Licensed under the Apache License, Version 2.0 (the "License");
006 * you may not use this file except in compliance with the License.
007 * 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 * Author:
018 * Franz Wilhelmstötter (franz.wilhelmstoetter@gmx.at)
019 */
020 package org.jenetics.util;
021
022 import static java.lang.String.format;
023 import static java.util.Objects.requireNonNull;
024 import static org.jenetics.internal.util.object.eq;
025
026 import org.jenetics.internal.util.HashBuilder;
027
028 /**
029 * Abstract implementation of the {@link Accumulator} interface which defines a
030 * {@code samples} property which is incremented by the {@link #accumulate(Object)}
031 * method.
032 *
033 * @author <a href="mailto:franz.wilhelmstoetter@gmx.at">Franz Wilhelmstötter</a>
034 * @since 1.0
035 * @version 1.0 — <em>$Date: 2014-03-01 $</em>
036 */
037 public abstract class MappedAccumulator<T>
038 implements
039 Accumulator<T>,
040 Cloneable
041 {
042
043 /**
044 * The number of accumulated samples.
045 */
046 protected long _samples = 0;
047
048 protected MappedAccumulator() {
049 }
050
051 /**
052 * Return the number of samples accumulated so far.
053 *
054 * @return the number of samples accumulated so far.
055 */
056 public long getSamples() {
057 return _samples;
058 }
059
060 @Override
061 public void accumulate(final T value) {
062 ++_samples;
063 }
064
065 /**
066 * Return a view of this adapter with a different type {@code B}.
067 *
068 * Usage example:
069 * [code]
070 * // Convert a string on the fly into a double value.
071 * final Converter<String, Double> converter = new Converter<String, Double>() {
072 * public Double convert(final String value) {
073 * return Double.valueOf(value);
074 * }
075 * };
076 *
077 * // The values to accumulate
078 * final List<String> values = Arrays.asList("0", "1", "2", "3", "4", "5");
079 *
080 * final Accumulators.Min<Double> accumulator = new Accumulators.Min<Double>();
081 *
082 * // No pain to accumulate collections of a different type.
083 * Accumulators.accumulate(values, accumulator.map(converter));
084 * [/code]
085 *
086 * @param <B> the type of the returned adapter (view).
087 * @param mapper the mapper needed to map between the type of this
088 * adapter and the adapter view type.
089 * @return the adapter view with the different type.
090 * @throws NullPointerException if the given {@code converter} is {@code null}.
091 */
092 public <B> MappedAccumulator<B> map(final Function<? super B, ? extends T> mapper) {
093 requireNonNull(mapper, "Mapper");
094 return new MappedAccumulator<B>() {
095 @Override
096 public void accumulate(final B value) {
097 MappedAccumulator.this.accumulate(mapper.apply(value));
098 }
099 };
100 }
101
102 @Override
103 public int hashCode() {
104 return HashBuilder.of(getClass()).and(_samples).value();
105 }
106
107 @Override
108 public boolean equals(final Object obj) {
109 if (obj == this) {
110 return true;
111 }
112 if (obj == null || getClass() != obj.getClass()) {
113 return false;
114 }
115
116 final MappedAccumulator<?> accumulator = (MappedAccumulator<?>)obj;
117 return eq(_samples, accumulator._samples);
118 }
119
120 @Override
121 public String toString() {
122 return format(
123 "%s[samples=%d]", getClass().getName(), _samples
124 );
125 }
126
127 @SuppressWarnings("unchecked")
128 @Override
129 protected MappedAccumulator<T> clone() {
130 try {
131 return (MappedAccumulator<T>)super.clone();
132 } catch (CloneNotSupportedException e) {
133 throw new AssertionError(e);
134 }
135 }
136
137 }
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