001 /*
002 * Java Genetic Algorithm Library (jenetics-3.8.0).
003 * Copyright (c) 2007-2017 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.util.Objects.requireNonNull;
023
024 import java.io.Serializable;
025 import java.time.Clock;
026 import java.time.Instant;
027 import java.time.ZoneId;
028 import java.time.ZoneOffset;
029
030 import org.jenetics.internal.util.Equality;
031
032 /**
033 * Clock implementation with <i>nano</i> second precision.
034 *
035 * @author <a href="mailto:franz.wilhelmstoetter@gmx.at">Franz Wilhelmstötter</a>
036 * @since 3.1
037 * @version 3.1
038 */
039 public final class NanoClock extends Clock implements Serializable {
040
041 private static final long serialVersionUID = 1L;
042
043 private static final long EPOCH_NANOS = System.currentTimeMillis()*1_000_000;
044 private static final long NANO_START = System.nanoTime();
045
046 private static final NanoClock UTC_INSTANCE = new NanoClock(ZoneOffset.UTC);
047
048 private static final NanoClock DEFAULT_INSTANCE =
049 new NanoClock(ZoneId.systemDefault());
050
051 /**
052 * This constants holds the number of nano seconds of one second.
053 */
054 public static final long NANOS_PER_SECOND = 1_000_000_000;
055
056 private final ZoneId _zone;
057
058 private NanoClock(final ZoneId zone) {
059 _zone = requireNonNull(zone, "zone");
060 }
061
062 @Override
063 public ZoneId getZone() {
064 return _zone;
065 }
066
067 @Override
068 public NanoClock withZone(final ZoneId zone) {
069 return zone.equals(_zone) ? this : new NanoClock(zone);
070 }
071
072 @Override
073 public long millis() {
074 return System.currentTimeMillis();
075 }
076
077 /**
078 * This returns the nanosecond-based instant, measured from
079 * 1970-01-01T00:00Z (UTC). This method will return valid values till the
080 * year 2262.
081 *
082 * @return the nanosecond-based instant, measured from 1970-01-01T00:00Z (UTC)
083 */
084 public long nanos() {
085 return System.nanoTime() - NANO_START + EPOCH_NANOS;
086 }
087
088 @Override
089 public Instant instant() {
090 final long now = nanos();
091 return Instant.ofEpochSecond(now/NANOS_PER_SECOND, now%NANOS_PER_SECOND);
092 }
093
094 @Override
095 public int hashCode() {
096 return _zone.hashCode() + 11;
097 }
098
099 @Override
100 public boolean equals(Object obj) {
101 return Equality.of(this, obj)
102 .test(clock -> _zone.equals(clock._zone));
103 }
104
105 @Override
106 public String toString() {
107 return "NanoClock[" + _zone + "]";
108 }
109
110 /**
111 * This clock is based on the <i>nano</i> system clock. It uses
112 * {@link System#nanoTime()} resolution
113 * <p>
114 * Conversion from instant to date or time uses the specified time-zone.
115 * <p>
116 * The returned implementation is immutable, thread-safe and
117 * {@code Serializable}.
118 *
119 * @param zone the time-zone to use to convert the instant to date-time
120 * @return a clock that uses the best available system clock in the
121 * specified zone
122 * @throws java.lang.NullPointerException if the given {@code zone} is
123 * {@code null}
124 */
125 public static NanoClock system(final ZoneId zone) {
126 return new NanoClock(zone);
127 }
128
129 /**
130 * This clock is based on the <i>nano</i> system clock. It uses
131 * {@link System#nanoTime()} resolution
132 * <p>
133 * Conversion from instant to date or time uses the specified time-zone.
134 * <p>
135 * The returned implementation is immutable, thread-safe and
136 * {@code Serializable}.
137 *
138 * @return a clock that uses the best available system clock in the
139 * UTC zone
140 * @throws java.lang.NullPointerException if the given {@code zone} is
141 * {@code null}
142 */
143 public static NanoClock systemUTC() {
144 return UTC_INSTANCE;
145 }
146
147 /**
148 * This clock is based on the <i>nano</i> system clock. It uses
149 * {@link System#nanoTime()} resolution
150 * <p>
151 * Conversion from instant to date or time uses the specified time-zone.
152 * <p>
153 * The returned implementation is immutable, thread-safe and
154 * {@code Serializable}.
155 *
156 * @return a clock that uses the best available system clock in the
157 * default zone
158 * @throws java.lang.NullPointerException if the given {@code zone} is
159 * {@code null}
160 */
161 public static NanoClock systemDefaultZone() {
162 return DEFAULT_INSTANCE;
163 }
164
165 }
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