8373566: Performance regression with java.text.MessageFormat subformat patterns

Reviewed-by: liach, rriggs, naoto

Author: Justin Lu

src/java.base/share/classes/java/text/MessageFormat.java

@@ -1713,12 +1713,7 @@ private Format formatFromPattern(String type, String style) {
             throw new IllegalArgumentException("unknown format type: " + type);
         }
         // Get the style if recognized, otherwise treat style as a SubformatPattern
-        FormatStyle fStyle;
-        try {
-            fStyle = FormatStyle.fromString(style);
-        } catch (IllegalArgumentException iae) {
-            fStyle = FormatStyle.SUBFORMATPATTERN;
-        }
+        FormatStyle fStyle = FormatStyle.fromString(style);
         return switch (fType) {
             case NUMBER -> switch (fStyle) {
                 case DEFAULT -> NumberFormat.getInstance(locale);
@@ -1976,41 +1971,43 @@ private enum FormatType {
     }
 
     // Corresponding to the FormatStyle pattern
+    // WARNING: fromString is dependent on ordinal positioning and Enum names.
     private enum FormatStyle {
-        DEFAULT(""),
-        SHORT("short"),
-        MEDIUM("medium"),
-        LONG("long"),
-        FULL("full"),
-        INTEGER("integer"),
-        CURRENCY("currency"),
-        PERCENT("percent"),
-        COMPACT_SHORT("compact_short"),
-        COMPACT_LONG("compact_long"),
-        OR("or"),
-        UNIT("unit"),
-        SUBFORMATPATTERN(null);
-
-        private final String text;
-
-        // Differs from FormatType in that the text String is
-        // not guaranteed to match the Enum name, thus a text field is used
-        FormatStyle(String text) {
-            this.text = text;
-        }
-
-        // This method returns a FormatStyle (excluding SUBFORMATPATTERN)
-        // that matches the passed String. If no FormatStyle is found,
-        // an IllegalArgumentException is thrown
+        // Special styles
+        DEFAULT,
+        SUBFORMATPATTERN,
+        // Pre-defined styles
+        SHORT,
+        MEDIUM,
+        LONG,
+        FULL,
+        INTEGER,
+        CURRENCY,
+        PERCENT,
+        COMPACT_SHORT,
+        COMPACT_LONG,
+        OR,
+        UNIT;
+
+        // Returns a FormatStyle corresponding to the input text.
+        // DEFAULT is the empty String.
+        // Pre-defined styles are lower case versions of their enum name
+        // (but compared case-insensitive for historical compatibility).
+        // SUBFORMATPATTERN is anything else.
         private static FormatStyle fromString(String text) {
-            for (FormatStyle style : values()) {
-                // Also check trimmed case-insensitive for historical reasons
-                if (style != FormatStyle.SUBFORMATPATTERN &&
-                        text.trim().compareToIgnoreCase(style.text) == 0) {
-                    return style;
+            var style = text.trim();
+            if (style.isEmpty()) {
+                return FormatStyle.DEFAULT;
+            }
+            var styles = values();
+            // Match starting at the pre-defined styles -> [SHORT:]
+            for (int i = SHORT.ordinal(); i < styles.length; i++) {
+                var fStyle = styles[i];
+                if (style.compareToIgnoreCase(fStyle.name()) == 0) {
+                    return fStyle;
                 }
             }
-            throw new IllegalArgumentException();
+            return FormatStyle.SUBFORMATPATTERN;
         }
     }
 

test/micro/org/openjdk/bench/java/text/MessageFormatterBench.java

@@ -1,4 +1,5 @@
 /*
+ * Copyright (c) 2025, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2024, Alibaba Group Holding Limited. All Rights Reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
@@ -51,6 +52,8 @@
 public class MessageFormatterBench {
 
     private Object[][] values;
+    private String choicePattern;
+    private String numberPattern;
 
     @Setup
     public void setup() {
@@ -60,6 +63,8 @@ public void setup() {
                 new Object[]{Double.valueOf(123.89), "MyDisk3"},
                 new Object[]{Long.valueOf(1234567), "MyDisk4"},
         };
+        choicePattern = "{0,choice,0#|1#{1}|2#{1} ({2})}";
+        numberPattern = "{0,number,000}";
     }
 
     private MessageFormat messageFormat = new MessageFormat("There is {0} GB of free space on the {1}.", Locale.ENGLISH);
@@ -72,6 +77,16 @@ public void testMessageFormat(final Blackhole bh) {
         }
     }
 
+    @Benchmark
+    public MessageFormat testSubformatChoice() {
+        return new MessageFormat(choicePattern);
+    }
+
+    @Benchmark
+    public MessageFormat testSubformatNumber() {
+        return new MessageFormat(numberPattern);
+    }
+
     public static void main(String... args) throws Exception {
         Options opts = new OptionsBuilder().include(MessageFormatterBench.class.getSimpleName()).shouldDoGC(true).build();
         new Runner(opts).run();