8318569: Add getter methods for Locale and Patterns in ListFormat

Reviewed-by: joehw, rriggs, iris, mli

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

@@ -322,6 +322,26 @@ public final class ListFormat extends Format {
         return new ListFormat(Locale.ROOT, Arrays.copyOf(patterns, PATTERN_ARRAY_LENGTH));
     }
 
+    /**
+     * {@return the {@code Locale} of this ListFormat}
+     *
+     * The {@code locale} is defined by {@link #getInstance(Locale, Type, Style)} or
+     * {@link #getInstance(String[])}.
+     */
+    public Locale getLocale() {
+        return locale;
+    }
+
+    /**
+     * {@return the patterns used in this ListFormat}
+     *
+     * The {@code patterns} are defined by {@link #getInstance(Locale, Type, Style)} or
+     * {@link #getInstance(String[])}.
+     */
+    public String[] getPatterns() {
+        return Arrays.copyOf(patterns, patterns.length);
+    }
+
     /**
      * {@return the string that consists of the input strings, concatenated with the
      * patterns of this {@code ListFormat}}

test/jdk/java/text/Format/ListFormat/TestListFormat.java

@@ -23,7 +23,7 @@
 
 /*
  * @test
- * @bug 8041488 8316974
+ * @bug 8041488 8316974 8318569
  * @summary Tests for ListFormat class
  * @run junit TestListFormat
  */
@@ -200,6 +200,7 @@ public class TestListFormat {
                 arguments(CUSTOM_PATTERNS_MINIMAL, SAMPLE4),
         };
     }
+
     static Arguments[] getInstance_3Arg_InheritPatterns() {
         return new Arguments[] {
                 arguments(ListFormat.Type.STANDARD, ListFormat.Style.FULL),
@@ -213,6 +214,17 @@ public class TestListFormat {
                 arguments(ListFormat.Type.UNIT, ListFormat.Style.NARROW),
         };
     }
+
+    static Arguments[] getLocale_localeDependent() {
+        return new Arguments[] {
+                arguments(Locale.ROOT),
+                arguments(Locale.US),
+                arguments(Locale.GERMANY),
+                arguments(Locale.JAPAN),
+                arguments(Locale.SIMPLIFIED_CHINESE),
+        };
+    }
+
     @ParameterizedTest
     @MethodSource
     void getInstance_1Arg(String[] patterns, List<String> input, String expected) throws ParseException {
@@ -235,6 +247,33 @@ public class TestListFormat {
         compareResult(f, SAMPLE3, expected, roundTrip);
     }
 
+    @Test
+    void getLocale_invariant() {
+        var f = ListFormat.getInstance(CUSTOM_PATTERNS_FULL);
+        assertEquals(Locale.ROOT, f.getLocale());
+    }
+
+    @Test
+    void getLocale_default() {
+        var f = ListFormat.getInstance();
+        assertEquals(Locale.getDefault(Locale.Category.FORMAT), f.getLocale());
+    }
+
+    @ParameterizedTest
+    @MethodSource
+    void getLocale_localeDependent(Locale l) {
+        var f = ListFormat.getInstance(l, ListFormat.Type.STANDARD, ListFormat.Style.FULL);
+        assertEquals(l, f.getLocale());
+    }
+
+    @Test
+    void getPatterns_immutability() {
+        var f = ListFormat.getInstance(CUSTOM_PATTERNS_FULL);
+        var p = f.getPatterns();
+        p[0] = null;
+        assertArrayEquals(CUSTOM_PATTERNS_FULL, f.getPatterns());
+    }
+
     @Test
     void format_3Arg() {
         var f = ListFormat.getInstance();