Fix some cases of formatting numbers

teavm-classlib/src/main/java/org/teavm/classlib/java/text/TDecimalFormat.java

@@ -241,8 +241,8 @@ public class TDecimalFormat extends TNumberFormat {
         buffer.append(positive ? positivePrefix : negativePrefix);
 
         // Add insignificant integer zeros
-        int digitPos = exponent;
         int intLength = Math.max(0, exponent);
+        int digitPos = Math.max(intLength, getMinimumIntegerDigits()) - 1;
         for (int i = getMinimumIntegerDigits() - 1; i >= intLength; --i) {
             buffer.append('0');
             if (groupingSize > 0 && digitPos % groupingSize == 0 && digitPos > 0) {
@@ -275,20 +275,24 @@ public class TDecimalFormat extends TNumberFormat {
             --digitPos;
         }
 
-        if (digitPos == 0 && getMinimumFractionDigits() == 0) {
+        if (mantissa == 0) {
-            if (isDecimalSeparatorAlwaysShown()) {
+            if (getMinimumFractionDigits() == 0) {
+                if (isDecimalSeparatorAlwaysShown()) {
+                    buffer.append(symbols.getDecimalSeparator());
+                }
+            } else {
                 buffer.append(symbols.getDecimalSeparator());
+                for (int i = 0; i < getMinimumFractionDigits(); ++i) {
+                    buffer.append('0');
+                }
             }
         } else {
             buffer.append(symbols.getDecimalSeparator());
 
             // Add significant fractional zeros
-            int fracZeros = Math.min(getMinimumFractionDigits(), Math.max(0, -exponent));
+            int fracZeros = Math.min(getMaximumFractionDigits(), Math.max(0, -exponent));
             digitPos = 0;
             for (int i = 0; i < fracZeros; ++i) {
-                if (groupingSize > 0 && digitPos % groupingSize == 0 && digitPos > 0) {
-                    buffer.append(symbols.getGroupingSeparator());
-                }
                 ++digitPos;
                 buffer.append('0');
             }
@@ -299,9 +303,6 @@ public class TDecimalFormat extends TNumberFormat {
                 if (mantissa == 0) {
                     break;
                 }
-                if (groupingSize > 0 && digitPos % groupingSize == 0 && digitPos > 0) {
-                    buffer.append(symbols.getGroupingSeparator());
-                }
                 ++digitPos;
                 long mantissaDigitMask = POW10_ARRAY[mantissaDigit];
                 buffer.append(Character.forDigit((int)(mantissa / mantissaDigitMask), 10));
@@ -311,9 +312,6 @@ public class TDecimalFormat extends TNumberFormat {
 
             // Add insignificant fractional zeros
             for (int i = digitPos; i < getMinimumFractionDigits(); ++i) {
-                if (groupingSize > 0 && digitPos % groupingSize == 0 && digitPos > 0) {
-                    buffer.append(symbols.getGroupingSeparator());
-                }
                 ++digitPos;
                 buffer.append('0');
             }
@@ -395,6 +393,9 @@ public class TDecimalFormat extends TNumberFormat {
     }
 
     private long normalize(long value) {
+        if (value >= MANTISSA_PATTERN * 10) {
+            value /= 10;
+        }
         if (value < MANTISSA_PATTERN / 1_000_0000_0000_0000L) {
             value *= 1_0000_0000_0000_0000L;
         }

teavm-tests/src/test/java/org/teavm/classlib/java/text/DecimalFormatTest.java

@@ -113,6 +113,15 @@ public class DecimalFormatTest {
         assertEquals(0, format.getMaximumFractionDigits());
     }
 
+    @Test
+    public void formatsIntegerPart() {
+        DecimalFormat format = createFormat("00");
+        assertEquals("02", format.format(2));
+        assertEquals("23", format.format(23));
+        assertEquals("23", format.format(23.2));
+        assertEquals("24", format.format(23.7));
+    }
+
     @Test
     public void formatsNumber() {
         DecimalFormat format = createFormat("0.0");
@@ -138,7 +147,6 @@ public class DecimalFormatTest {
     @Test
     public void formatsFractionalPart() {
         DecimalFormat format = createFormat("0.0000####");
-
         assertEquals("0.00001235", format.format(0.0000123456));
         assertEquals("0.00012346", format.format(0.000123456));
         assertEquals("0.00123456", format.format(0.00123456));
@@ -147,6 +155,12 @@ public class DecimalFormatTest {
         assertEquals("0.1230", format.format(0.123));
         assertEquals("0.1234", format.format(0.1234));
         assertEquals("0.12345", format.format(0.12345));
+
+        format = createFormat("0.##");
+        assertEquals("23", format.format(23));
+        assertEquals("2.3", format.format(2.3));
+        assertEquals("0.23", format.format(0.23));
+        assertEquals("0.02", format.format(0.023));
     }
 
     @Test
@@ -202,6 +216,24 @@ public class DecimalFormatTest {
         assertEquals("-4", format.format(-3.5));
     }
 
+    @Test
+    public void formatsWithGroups() {
+        DecimalFormat format = createFormat("#,###.0");
+        assertEquals("23.0", format.format(23));
+        assertEquals("2,300.0", format.format(2300));
+        assertEquals("2,300,000,000,000,000,000,000.0", format.format(23E20));
+        assertEquals("23,000,000,000,000,000,000,000,000.0", format.format(23E24));
+
+        format = createFormat("000,000,000,000,000,000,000");
+        assertEquals("000,000,000,000,000,000,023", format.format(23));
+    }
+
+    @Test
+    public void formatsLargeValues() {
+        DecimalFormat format = createFormat("0");
+        assertEquals("9223372036854775807", format.format(9223372036854775807L));
+    }
+
     private DecimalFormat createFormat(String format) {
         return new DecimalFormat(format, symbols);
     }