8368328: CompactNumberFormat.clone does not produce independent instances

Reviewed-by: rgiulietti, jlu

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

@@ -250,38 +250,43 @@ public final class CompactNumberFormat extends NumberFormat {
 
     /**
      * List of positive prefix patterns of this formatter's
-     * compact number patterns.
+     * compact number patterns. This field is a read-only
+     * constant once initialized.
      */
     private transient List<Patterns> positivePrefixPatterns;
 
     /**
      * List of negative prefix patterns of this formatter's
-     * compact number patterns.
+     * compact number patterns. This field is a read-only
+     * constant once initialized.
      */
     private transient List<Patterns> negativePrefixPatterns;
 
     /**
      * List of positive suffix patterns of this formatter's
-     * compact number patterns.
+     * compact number patterns. This field is a read-only
+     * constant once initialized.
      */
     private transient List<Patterns> positiveSuffixPatterns;
 
     /**
      * List of negative suffix patterns of this formatter's
-     * compact number patterns.
+     * compact number patterns. This field is a read-only
+     * constant once initialized.
      */
     private transient List<Patterns> negativeSuffixPatterns;
 
     /**
      * List of divisors of this formatter's compact number patterns.
      * Divisor can be either Long or BigInteger (if the divisor value goes
-     * beyond long boundary)
+     * beyond long boundary). This field is a read-only constant
+     * once initialized.
      */
     private transient List<Number> divisors;
 
     /**
      * List of place holders that represent minimum integer digits at each index
-     * for each count.
+     * for each count. This field is a read-only constant once initialized.
      */
     private transient List<Patterns> placeHolderPatterns;
 
@@ -374,7 +379,7 @@ public final class CompactNumberFormat extends NumberFormat {
 
     /**
      * The map for plural rules that maps LDML defined tags (e.g. "one") to
-     * its rule.
+     * its rule. This field is a read-only constant once initialized.
      */
     private transient Map<String, String> rulesMap;
 
@@ -1515,7 +1520,7 @@ public final class CompactNumberFormat extends NumberFormat {
         }
     }
 
-    private final transient DigitList digitList = new DigitList();
+    private transient DigitList digitList = new DigitList();
     private static final int STATUS_INFINITE = 0;
     private static final int STATUS_POSITIVE = 1;
     private static final int STATUS_LENGTH   = 2;
@@ -2506,8 +2511,14 @@ public final class CompactNumberFormat extends NumberFormat {
     @Override
     public CompactNumberFormat clone() {
         CompactNumberFormat other = (CompactNumberFormat) super.clone();
+
+        // Cloning reference fields. Other fields (e.g., "positivePrefixPatterns")
+        // are not cloned since they are read-only constants after initialization.
         other.compactPatterns = compactPatterns.clone();
         other.symbols = (DecimalFormatSymbols) symbols.clone();
+        other.decimalFormat = (DecimalFormat) decimalFormat.clone();
+        other.defaultDecimalFormat = (DecimalFormat) defaultDecimalFormat.clone();
+        other.digitList = (DigitList) digitList.clone();
         return other;
     }
 

test/jdk/java/text/Format/CompactNumberFormat/TestClone.java

@@ -0,0 +1,95 @@
+/*
+ * Copyright (c) 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
+ * 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.
+ */
+/*
+ * @test
+ * @bug 8368328
+ * @summary Tests if CompactNumberFormat.clone() creates an independent object
+ * @run junit/othervm --add-opens java.base/java.text=ALL-UNNAMED TestClone
+ */
+
+import java.lang.invoke.MethodHandles;
+import java.text.CompactNumberFormat;
+import java.text.DecimalFormat;
+import java.text.DecimalFormatSymbols;
+import java.text.NumberFormat;
+import java.util.Locale;
+import java.util.stream.IntStream;
+import java.util.stream.Stream;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotSame;
+
+public class TestClone {
+    // Concurrently parse numbers using cloned instances as originally
+    // reported in the bug. This test could produce false negative results,
+    // depending on the testing environment
+    @Test
+    void randomAccessTest() {
+        var original =
+            NumberFormat.getCompactNumberInstance(Locale.US, NumberFormat.Style.SHORT);
+        var threads = IntStream.range(0, 10)
+            .mapToObj(num -> new Thread(() -> {
+                var clone = (NumberFormat) original.clone();
+                for (int i = 0; i < 1000; i++) {
+                    assertDoesNotThrow(() ->
+                        assertEquals(num, clone.parse(String.valueOf(num)).intValue()));
+                }
+            })).toList();
+        threads.forEach(Thread::start);
+        threads.forEach(t -> {
+            try {
+                t.join();
+            } catch (InterruptedException ie) {
+                throw new RuntimeException(ie);
+            }
+        });
+    }
+
+    private static Stream<Arguments> referenceFields() throws ClassNotFoundException {
+        return Stream.of(
+            Arguments.of("compactPatterns", String[].class),
+            Arguments.of("symbols", DecimalFormatSymbols.class),
+            Arguments.of("decimalFormat", DecimalFormat.class),
+            Arguments.of("defaultDecimalFormat", DecimalFormat.class),
+            Arguments.of("digitList", Class.forName("java.text.DigitList"))
+        );
+    }
+    // Explicitly checks if the cloned object has its own references for
+    // "compactPatterns", "symbols", "decimalFormat", "defaultDecimalFormat",
+    // and "digitList"
+    @ParameterizedTest
+    @MethodSource("referenceFields")
+    void whiteBoxTest(String fieldName, Class<?> type) throws Throwable {
+        var original = NumberFormat.getCompactNumberInstance(Locale.US, NumberFormat.Style.SHORT);
+        var clone = original.clone();
+        var lookup = MethodHandles.privateLookupIn(CompactNumberFormat.class, MethodHandles.lookup());
+
+        assertNotSame(lookup.findGetter(CompactNumberFormat.class, fieldName, type).invoke(original),
+            lookup.findGetter(CompactNumberFormat.class, fieldName, type).invoke(clone));
+    }
+}