use EnumMap

Author: wenshao

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 +2580,23 @@ 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 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

@@ -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

@@ -98,6 +98,7 @@
 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;
@@ -125,10 +126,21 @@
 final class Parsed implements TemporalAccessor {
     // some fields are accessed using package scope from DateTimeParseContext
 
+    final boolean onlyChronoField;
+    @SuppressWarnings("unchecked")
+    private Map<TemporalField, Long> createFieldValuesMap() {
+        if (onlyChronoField) {
+            return new HashMap<>();
+        } else {
+            // Create the EnumMap with raw types and cast it appropriately
+            // This is safe because ChronoField implements TemporalField
+            return (Map<TemporalField, Long>) (Map) new EnumMap<>(ChronoField.class);
+        }
+    }
     /**
      * The parsed fields.
      */
-    final Map<TemporalField, Long> fieldValues = new HashMap<>();
+    final Map<TemporalField, Long> fieldValues = createFieldValuesMap();
     /**
      * The parsed zone.
      */
@@ -169,15 +181,16 @@ final class Parsed implements TemporalAccessor {
     /**
      * Creates an instance.
      */
-    Parsed() {
+    Parsed(boolean onlyChronoField) {
+        this.onlyChronoField = onlyChronoField;
     }
 
     /**
      * Creates a copy.
      */
     Parsed copy() {
         // only copy fields used in parsing stage
-        Parsed cloned = new Parsed();
+        Parsed cloned = new Parsed(onlyChronoField);
         cloned.fieldValues.putAll(this.fieldValues);
         cloned.zone = this.zone;
         cloned.zoneNameType = this.zoneNameType;