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Nicolai Parlog
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[06] Create benchmark for OffestDateTime::parse
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‎src/main/java/org/codefx/demo/effective_java/_06_unnecessary_objects/OffsetDateTimeParse.java‎

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package org.codefx.demo.effective_java._06_unnecessary_objects;
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import java.time.LocalDate;
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import java.time.LocalTime;
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import java.time.OffsetDateTime;
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import java.time.OffsetTime;
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import java.time.ZoneOffset;
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import org.openjdk.jmh.annotations.Benchmark;
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import org.openjdk.jmh.annotations.Fork;
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import org.openjdk.jmh.annotations.Measurement;
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import org.openjdk.jmh.annotations.Warmup;
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//@Fork(value = 2, jvmArgsAppend = "-Djmh.stack.lines=3")
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//@Warmup(iterations = 5, time = 2)
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//@Measurement(iterations = 7, time = 2)
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public class OffsetDateTimeParse extends ObjectCreationBenchmarks {
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@Benchmark
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public Object parse() {
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// NOTE unnecessary object:
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// The `OffsetDateTime` parser uses a map to store parsed values,
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// which produces a measurable amount of garbage.
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// See https://bugs.openjdk.java.net/browse/JDK-8213243 for details.
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return OffsetDateTime.parse("2001-02-03T04:05:06.789+01:00");
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}
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@Benchmark
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public Object handwrittenParser() {
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return OffsetDateTimeParser.offsetDateTime("2001-02-03T04:05:06.789+01:00");
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}
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/**
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* This class was written by Lukas Eder and attached to JDK-8213243
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* (https://bugs.openjdk.java.net/browse/JDK-8213243)
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* to demonstrate a faster parser than {@link OffsetDateTime#parse(CharSequence)}.
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*/
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static final class OffsetDateTimeParser {
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static final OffsetTime offsetTime(String string) {
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if (string == null)
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return null;
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// Out parameter emulation
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int[] position = { 0 };
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return OffsetTime.of(parseLocalTime(string, position), parseOffset(string, position));
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}
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static final OffsetDateTime offsetDateTime(String string) {
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if (string == null)
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return null;
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// Out parameter emulation
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int[] position = { 0 };
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LocalDate d = parseLocalDate(string, position);
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// [#4338] SQL supports the alternative ISO 8601 date format, where a
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// whitespace character separates date and time. java.time does not
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parseAnyChar(string, position, " T");
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LocalTime t = parseLocalTime(string, position);
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return OffsetDateTime.of(d, t, parseOffset(string, position));
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}
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static final LocalDate parseLocalDate(String string, int[] position) {
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int year = parseInt(string, position, 4);
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parseChar(string, position, '-');
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int month = parseInt(string, position, 2);
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parseChar(string, position, '-');
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int day = parseInt(string, position, 2);
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return LocalDate.of(year, month, day);
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}
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static final LocalTime parseLocalTime(String string, int[] position) {
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int hour = parseInt(string, position, 2);
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// [#5895] HSQLDB seems to confuse 00:00:00+02:00 with 24:00:00+02:00
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// https://sourceforge.net/p/hsqldb/bugs/1523/
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if (hour == 24)
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hour = hour % 24;
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parseChar(string, position, ':');
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int minute = parseInt(string, position, 2);
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int second = 0;
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int nano = 0;
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if (parseCharIf(string, position, ':')) {
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second = parseInt(string, position, 2);
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if (parseCharIf(string, position, '.')) {
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nano = 1000000 * parseInt(string, position, 3);
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if (Character.isDigit(string.charAt(position[0]))) {
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nano = nano + 1000 * parseInt(string, position, 3);
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if (Character.isDigit(string.charAt(position[0]))) {
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nano = nano + parseInt(string, position, 3);
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}
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}
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}
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}
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return LocalTime.of(hour, minute, second, nano);
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}
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private static final ZoneOffset parseOffset(String string, int[] position) {
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int offsetHours = 0;
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int offsetMinutes = 0;
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if (!parseCharIf(string, position, 'Z')) {
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// [#4965] Oracle might return some spare space
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while (parseCharIf(string, position, ' '))
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;
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boolean minus = parseCharIf(string, position, '-');
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boolean plus = !minus && parseCharIf(string, position, '+');
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if (minus || plus) {
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offsetHours = parseInt(string, position, 1);
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// [#4965] Oracle might return a single-digit hour offset
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if (Character.isDigit(string.charAt(position[0])))
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offsetHours = offsetHours * 10 + parseInt(string, position, 1);
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// [#4338] [#5180] [#5776] PostgreSQL is more lenient regarding the offset format
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if (parseCharIf(string, position, ':'))
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offsetMinutes = parseInt(string, position, 2);
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}
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}
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return ZoneOffset.ofHoursMinutes(offsetHours, offsetMinutes);
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}
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private static final void parseAnyChar(String string, int[] position, String expected) {
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for (int i = 0; i < expected.length(); i++) {
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if (string.charAt(position[0]) == expected.charAt(i)) {
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position[0] = position[0] + 1;
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return;
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}
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}
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throw new IllegalArgumentException("Expected any of \"" + expected + "\" at position " + position[0] + " in " + string);
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}
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private static final boolean parseCharIf(String string, int[] position, char expected) {
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boolean result = string.length() > position[0] && string.charAt(position[0]) == expected;
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if (result)
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position[0] = position[0] + 1;
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return result;
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}
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private static final void parseChar(String string, int[] position, char expected) {
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if (!parseCharIf(string, position, expected))
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throw new IllegalArgumentException("Expected '" + expected + "' at position " + position[0] + " in " + string);
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}
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private static final int parseInt(String string, int[] position, int length) {
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int result = 0;
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for (int i = position[0] + length - 1, dec = 1; i >= position[0]; i--, dec = dec * 10) {
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int digit = string.charAt(i) - '0';
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if (digit >= 0 && digit < 10)
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result = result + dec * digit;
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else
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throw new NumberFormatException("Not a number: " + string);
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}
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position[0] = position[0] + length;
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return result;
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}
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}
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}

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