8372460: Use EnumMap instead of HashMap for DateTimeFormatter parsing to improve performance

src/java.base/share/classes/java/time/format/DateTimeFormatter.java

@@ -544,6 +544,12 @@ public final class DateTimeFormatter {
      */
     private final ZoneId zone;
 
+    /**
+     * Flag indicating whether this formatter only uses ChronoField instances.
+     * This is used to optimize the storage of parsed field values in the Parsed class.
+     */
+    final boolean onlyChronoField;
+
     //-----------------------------------------------------------------------
     /**
      * Creates a formatter using the specified pattern.
@@ -1486,6 +1492,7 @@ public static final TemporalQuery<Boolean> parsedLeapSecond() {
         this.resolverStyle = Objects.requireNonNull(resolverStyle, "resolverStyle");
         this.chrono = chrono;
         this.zone = zone;
+        this.onlyChronoField = printerParser.onlyChronoField();
     }
 
     //-----------------------------------------------------------------------

src/java.base/share/classes/java/time/format/DateTimeFormatterBuilder.java

@@ -2580,6 +2580,24 @@ public int parse(DateTimeParseContext context, CharSequence text, int position)
             }
         }
 
+        /**
+         * Checks whether this composite printer parser only uses ChronoField instances.
+         * This is used to optimize the storage of parsed field values in the Parsed class.
+         *
+         * @return true if all printer parsers in this composite only use ChronoField instances,
+         *         false otherwise
+         */
+        boolean onlyChronoField() {
+            for (DateTimePrinterParser pp : printerParsers) {
+                if ((pp instanceof NumberPrinterParser    npp && !(npp.field instanceof ChronoField))
+                 || (pp instanceof TextPrinterParser      tpp && !(tpp.field instanceof ChronoField))
+                 || (pp instanceof CompositePrinterParser cpp && !cpp.onlyChronoField())) {
+                    return false;
+                }
+            }
+            return true;
+        }
+
         @Override
         public String toString() {
             StringBuilder buf = new StringBuilder();

src/java.base/share/classes/java/time/format/DateTimeParseContext.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2012, 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2012, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -120,7 +120,7 @@ final class DateTimeParseContext {
     DateTimeParseContext(DateTimeFormatter formatter) {
         super();
         this.formatter = formatter;
-        parsed.add(new Parsed());
+        parsed.add(new Parsed(formatter.onlyChronoField));
     }
 
     /**

src/java.base/share/classes/java/time/format/Parsed.java

@@ -1,5 +1,6 @@
 /*
- * Copyright (c) 2012, 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2012, 2025, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2025, Alibaba Group Holding Limited. All Rights Reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -98,6 +99,7 @@
 import java.time.temporal.TemporalQueries;
 import java.time.temporal.TemporalQuery;
 import java.time.temporal.UnsupportedTemporalTypeException;
+import java.util.EnumMap;
 import java.util.HashMap;
 import java.util.Iterator;
 import java.util.Map;
@@ -128,7 +130,7 @@ final class Parsed implements TemporalAccessor {
     /**
      * The parsed fields.
      */
-    final Map<TemporalField, Long> fieldValues = new HashMap<>();
+    final Map<TemporalField, Long> fieldValues;
     /**
      * The parsed zone.
      */
@@ -169,15 +171,20 @@ final class Parsed implements TemporalAccessor {
     /**
      * Creates an instance.
      */
-    Parsed() {
+    @SuppressWarnings("unchecked")
+    Parsed(boolean onlyChronoField) {
+        // Create the EnumMap with raw types and cast it appropriately
+        // This is safe because ChronoField implements TemporalField
+        fieldValues = onlyChronoField ? (Map<TemporalField, Long>) (Map) new EnumMap<>(ChronoField.class)
+                                      : new HashMap<>();
     }
 
     /**
      * Creates a copy.
      */
     Parsed copy() {
         // only copy fields used in parsing stage
-        Parsed cloned = new Parsed();
+        Parsed cloned = new Parsed(fieldValues instanceof EnumMap);
         cloned.fieldValues.putAll(this.fieldValues);
         cloned.zone = this.zone;
         cloned.zoneNameType = this.zoneNameType;

test/micro/org/openjdk/bench/java/time/format/DateTimeFormatterParse.java

@@ -0,0 +1,118 @@
+/*
+ * Copyright (c) 2025, Alibaba Group Holding Limited. All Rights Reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+package org.openjdk.bench.java.time.format;
+
+import java.time.Duration;
+import java.time.Instant;
+import java.time.LocalDate;
+import java.time.LocalDateTime;
+import java.time.LocalTime;
+import java.time.OffsetDateTime;
+import java.time.ZonedDateTime;
+import java.time.format.DateTimeFormatter;
+import java.time.temporal.ChronoUnit;
+
+import java.util.Locale;
+import java.util.Random;
+import java.util.TimeZone;
+import java.util.concurrent.TimeUnit;
+import java.util.stream.IntStream;
+import java.util.stream.Stream;
+
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Fork;
+import org.openjdk.jmh.annotations.Measurement;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+import org.openjdk.jmh.annotations.Param;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.Setup;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.annotations.Warmup;
+import org.openjdk.jmh.infra.Blackhole;
+
+@BenchmarkMode(Mode.Throughput)
+@OutputTimeUnit(TimeUnit.MILLISECONDS)
+@Warmup(iterations = 5, time = 1)
+@Measurement(iterations = 5, time = 1)
+@Fork(3)
+@State(Scope.Thread)
+public class DateTimeFormatterParse {
+    static final DateTimeFormatter formatterLocalTime = DateTimeFormatter.ofPattern("HH:mm:ss");
+    static final DateTimeFormatter formatterLocalTimeWithNano = DateTimeFormatter.ofPattern("HH:mm:ss.SSS");
+    static final DateTimeFormatter formatterLocalDate = DateTimeFormatter.ofPattern("yyyy-MM-dd");
+    static final DateTimeFormatter formatterLocalDateTime = DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss");
+    static final DateTimeFormatter formatterLocalDateTimeWithNano = DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss.SSS");
+    static final DateTimeFormatter formatterOffsetDateTime = DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss.SSSSSSZZZZZ");
+    static final DateTimeFormatter formatterZonedDateTime = DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss.SSSSSSZZZZZ'['VV']'");
+
+    static final String STR_LOCALTIME = "21:11:48";
+    static final String STR_LOCALTIME_WITH_NANO = "21:11:48.456";
+    static final String STR_LOCALDATE = "2024-08-01";
+    static final String STR_LOCALDATETIME = "2024-08-01T21:11:48";
+    static final String STR_LOCALDATETIME_WITH_NANO = "2024-08-01T21:11:48.456";
+    static final String STR_INSTANT = "2024-08-12T03:25:54.980339Z";
+    static final String STR_OFFSETDATETIME = "2024-08-12T11:50:46.731509+08:00";
+    static final String STR_ZONEDDATETIME = "2024-08-12T11:50:46.731509+08:00[Asia/Shanghai]";
+
+    @Benchmark
+    public LocalTime parseLocalTime() {
+        return LocalTime.parse(STR_LOCALTIME, formatterLocalTime);
+    }
+
+    @Benchmark
+    public LocalTime parseLocalTimeWithNano() {
+        return LocalTime.parse(STR_LOCALTIME_WITH_NANO, formatterLocalTimeWithNano);
+    }
+
+    @Benchmark
+    public LocalDate parseLocalDate() {
+        return LocalDate.parse(STR_LOCALDATE, formatterLocalDate);
+    }
+
+    @Benchmark
+    public LocalDateTime parseLocalDateTime() {
+        return LocalDateTime.parse(STR_LOCALDATETIME, formatterLocalDateTime);
+    }
+
+    @Benchmark
+    public LocalDateTime parseLocalDateTimeWithNano() {
+        return LocalDateTime.parse(STR_LOCALDATETIME_WITH_NANO, formatterLocalDateTimeWithNano);
+    }
+
+    @Benchmark
+    public OffsetDateTime parseOffsetDateTime() {
+        return OffsetDateTime.parse(STR_OFFSETDATETIME, formatterOffsetDateTime);
+    }
+
+    @Benchmark
+    public ZonedDateTime parseZonedDateTime() {
+        return ZonedDateTime.parse(STR_ZONEDDATETIME, formatterZonedDateTime);
+    }
+
+    @Benchmark
+    public Instant parseInstant() {
+        return Instant.parse(STR_INSTANT);
+    }
+}