src/java.base/share/classes/java/util/Formatter.java

*** 45,54 ****
--- 45,55 ----
  import java.nio.charset.UnsupportedCharsetException;
  import java.text.DateFormatSymbols;
  import java.text.DecimalFormat;
  import java.text.DecimalFormatSymbols;
  import java.text.NumberFormat;
+ import java.text.spi.NumberFormatProvider;
  import java.util.regex.Matcher;
  import java.util.regex.Pattern;
  import java.util.Objects;
  
  import java.time.DateTimeException;
*** 60,69 ****
--- 61,72 ----
  import java.time.temporal.TemporalQueries;
  import java.time.temporal.UnsupportedTemporalTypeException;
  
  import jdk.internal.math.DoubleConsts;
  import jdk.internal.math.FormattedFloatingDecimal;
+ import sun.util.locale.provider.LocaleProviderAdapter;
+ import sun.util.locale.provider.ResourceBundleBasedAdapter;
  
  /**
   * An interpreter for printf-style format strings.  This class provides support
   * for layout justification and alignment, common formats for numeric, string,
   * and date/time data, and locale-specific output.  Common Java types such as
*** 4474,4485 ****
                      grpSep = ',';
                      grpSize = 3;
                  } else {
                      DecimalFormatSymbols dfs = DecimalFormatSymbols.getInstance(l);
                      grpSep = dfs.getGroupingSeparator();
!                     DecimalFormat df = (DecimalFormat) NumberFormat.getIntegerInstance(l);
                      grpSize = df.getGroupingSize();
                  }
              }
  
              // localize the digits inserting group separators as necessary
              for (int j = offset; j < len; j++) {
--- 4477,4513 ----
                      grpSep = ',';
                      grpSize = 3;
                  } else {
                      DecimalFormatSymbols dfs = DecimalFormatSymbols.getInstance(l);
                      grpSep = dfs.getGroupingSeparator();
!                     DecimalFormat df = null;
!                     NumberFormat nf = NumberFormat.getNumberInstance(l);
!                     if (nf instanceof DecimalFormat) {
!                         df = (DecimalFormat) nf;
!                     } else {
! 
!                         // Use DecimalFormat constructor to obtain the instance,
!                         // in case NumberFormat.getNumberInstance(l)
!                         // returns instance other than DecimalFormat
!                         LocaleProviderAdapter adapter = LocaleProviderAdapter
!                                 .getAdapter(NumberFormatProvider.class, l);
!                         if (!(adapter instanceof ResourceBundleBasedAdapter)) {
!                             adapter = LocaleProviderAdapter.getResourceBundleBased();
!                         }
!                         String[] all = adapter.getLocaleResources(l)
!                                 .getNumberPatterns();
!                         df = new DecimalFormat(all[0], dfs);
!                     }
                      grpSize = df.getGroupingSize();
+                     // Some locales do not use grouping (the number
+                     // pattern for these locales does not contain group, e.g.
+                     // ("#0.###")), but specify a grouping separator.
+                     // To avoid unnecessary identification of the position of
+                     // grouping separator, reset its value with null character
+                     if (!df.isGroupingUsed() || grpSize == 0) {
+                         grpSep = '\0';
+                     }
                  }
              }
  
              // localize the digits inserting group separators as necessary
              for (int j = offset; j < len; j++) {