001 /*
002 * Java Genetic Algorithm Library (jenetics-4.0.0).
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@gmail.com)
019 */
020 package io.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 /**
031 * Clock implementation with <i>nano</i> second precision.
032 *
033 * @author <a href="mailto:franz.wilhelmstoetter@gmail.com">Franz Wilhelmstötter</a>
034 * @since 3.1
035 * @version 3.1
036 */
037 public final class NanoClock extends Clock implements Serializable {
038
039 private static final long serialVersionUID = 1L;
040
041 private static final long EPOCH_NANOS = System.currentTimeMillis()*1_000_000;
042 private static final long NANO_START = System.nanoTime();
043 private static final long OFFSET_NANOS = EPOCH_NANOS - NANO_START;
044
045 private static final NanoClock UTC_INSTANCE = new NanoClock(ZoneOffset.UTC);
046
047 private static final NanoClock DEFAULT_INSTANCE =
048 new NanoClock(ZoneId.systemDefault());
049
050 /**
051 * This constants holds the number of nano seconds of one second.
052 */
053 public static final long NANOS_PER_SECOND = 1_000_000_000;
054
055 private final ZoneId _zone;
056
057 private NanoClock(final ZoneId zone) {
058 _zone = requireNonNull(zone, "zone");
059 }
060
061 @Override
062 public ZoneId getZone() {
063 return _zone;
064 }
065
066 @Override
067 public NanoClock withZone(final ZoneId zone) {
068 return zone.equals(_zone) ? this : new NanoClock(zone);
069 }
070
071 @Override
072 public long millis() {
073 return System.currentTimeMillis();
074 }
075
076 /**
077 * This returns the nanosecond-based instant, measured from
078 * 1970-01-01T00:00Z (UTC). This method will return valid values till the
079 * year 2262.
080 *
081 * @return the nanosecond-based instant, measured from 1970-01-01T00:00Z (UTC)
082 */
083 public long nanos() {
084 return System.nanoTime() + OFFSET_NANOS;
085 }
086
087 @Override
088 public Instant instant() {
089 final long now = nanos();
090 return Instant.ofEpochSecond(now/NANOS_PER_SECOND, now%NANOS_PER_SECOND);
091 }
092
093 @Override
094 public int hashCode() {
095 return _zone.hashCode() + 11;
096 }
097
098 @Override
099 public boolean equals(Object obj) {
100 return obj instanceof NanoClock && ((NanoClock)obj)._zone.equals(_zone);
101 }
102
103 @Override
104 public String toString() {
105 return "NanoClock[" + _zone + "]";
106 }
107
108 /**
109 * This clock is based on the <i>nano</i> system clock. It uses
110 * {@link System#nanoTime()} resolution
111 * <p>
112 * Conversion from instant to date or time uses the specified time-zone.
113 * <p>
114 * The returned implementation is immutable, thread-safe and
115 * {@code Serializable}.
116 *
117 * @param zone the time-zone to use to convert the instant to date-time
118 * @return a clock that uses the best available system clock in the
119 * specified zone
120 * @throws java.lang.NullPointerException if the given {@code zone} is
121 * {@code null}
122 */
123 public static NanoClock system(final ZoneId zone) {
124 return new NanoClock(zone);
125 }
126
127 /**
128 * This clock is based on the <i>nano</i> system clock. It uses
129 * {@link System#nanoTime()} resolution
130 * <p>
131 * Conversion from instant to date or time uses the specified time-zone.
132 * <p>
133 * The returned implementation is immutable, thread-safe and
134 * {@code Serializable}.
135 *
136 * @return a clock that uses the best available system clock in the
137 * UTC zone
138 * @throws java.lang.NullPointerException if the given {@code zone} is
139 * {@code null}
140 */
141 public static NanoClock systemUTC() {
142 return UTC_INSTANCE;
143 }
144
145 /**
146 * This clock is based on the <i>nano</i> system clock. It uses
147 * {@link System#nanoTime()} resolution
148 * <p>
149 * Conversion from instant to date or time uses the specified time-zone.
150 * <p>
151 * The returned implementation is immutable, thread-safe and
152 * {@code Serializable}.
153 *
154 * @return a clock that uses the best available system clock in the
155 * default zone
156 * @throws java.lang.NullPointerException if the given {@code zone} is
157 * {@code null}
158 */
159 public static NanoClock systemDefaultZone() {
160 return DEFAULT_INSTANCE;
161 }
162
163 }
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