Added a constant for no pattern match

core/src/main/java/org/apache/calcite/util/format/PostgresqlDateTimeFormatter.java

@@ -39,6 +39,11 @@ private static class PatternConvertResult {
     final boolean matched;
     final String formattedString;
 
+    protected PatternConvertResult() {
+      matched = false;
+      formattedString = null;
+    }
+
     protected PatternConvertResult(boolean matched, String formattedString) {
       this.matched = matched;
       this.formattedString = formattedString;
@@ -90,7 +95,7 @@ protected NumberFormatPattern(Function<ZonedDateTime, String> converter, String.
       }
 
       if (patternToUse == null) {
-        return new PatternConvertResult(false, null);
+        return NO_PATTERN_MATCH;
       }
 
       parsePosition.setIndex(parsePosition.getIndex() + patternToUse.length());
@@ -217,16 +222,18 @@ protected StringFormatPattern(Function<ZonedDateTime, String> converter, String.
         }
       }
 
-      return new PatternConvertResult(false, null);
+      return NO_PATTERN_MATCH;
     }
   }
 
+  private static final PatternConvertResult NO_PATTERN_MATCH = new PatternConvertResult();
+
   /**
    * The format patterns that are supported. Order is very important, since some patterns
    * are prefixes of other patterns.
    */
   @SuppressWarnings("TemporalAccessorGetChronoField")
-  private static FormatPattern[] formatPatterns = new FormatPattern[] {
+  private static final FormatPattern[] FORMAT_PATTERNS = new FormatPattern[] {
       new NumberFormatPattern(
           dt -> {
             final int hour = dt.get(ChronoField.HOUR_OF_AMPM);
@@ -597,7 +604,7 @@ public static String toChar(String formatString, ZonedDateTime dateTime) {
     while (parsePosition.getIndex() < formatString.length()) {
       boolean matched = false;
 
-      for (FormatPattern formatPattern : formatPatterns) {
+      for (FormatPattern formatPattern : FORMAT_PATTERNS) {
         final PatternConvertResult patternConvertResult =
             formatPattern.convert(parsePosition, formatString, dateTime);
         if (patternConvertResult.matched) {