Fixed StringUtils.formatDecimal to work with decimals of 0.

src/androidTest/java/de/dennisguse/opentracks/util/StringUtilsTest.java

@@ -199,4 +199,24 @@ public class StringUtilsTest {
         Assert.assertEquals(-1, parts[1]);
         Assert.assertEquals(0, parts[2]);
     }
+
+    @Test
+    public void testFormatDecimal() {
+        Assert.assertEquals("0", StringUtils.formatDecimal(0.0, 0));
+        Assert.assertEquals("0", StringUtils.formatDecimal(0.1, 0));
+        Assert.assertEquals("1", StringUtils.formatDecimal(1.1, 0));
+        Assert.assertEquals("10", StringUtils.formatDecimal(10, 0));
+        Assert.assertEquals("10", StringUtils.formatDecimal(10.1, 0));
+        Assert.assertEquals("0", StringUtils.formatDecimal(-0.1, 0));
+
+        Assert.assertEquals("0", StringUtils.formatDecimal(0.0, 2));
+        Assert.assertEquals("0.1", StringUtils.formatDecimal(0.1, 2));
+        Assert.assertEquals("1.1", StringUtils.formatDecimal(1.1, 2));
+        Assert.assertEquals("10", StringUtils.formatDecimal(10, 2));
+        Assert.assertEquals("10.1", StringUtils.formatDecimal(10.1, 2));
+        Assert.assertEquals("10.11", StringUtils.formatDecimal(10.111, 2));
+        Assert.assertEquals("-0.1", StringUtils.formatDecimal(-0.1, 2));
+
+        Assert.assertEquals("1", StringUtils.formatDecimal(0.99, 1));
+    }
 }

src/main/java/de/dennisguse/opentracks/util/StringUtils.java

@@ -21,6 +21,7 @@ import android.text.TextUtils;
 import android.text.format.DateUtils;
 import android.util.Pair;
 
+import java.text.DecimalFormat;
 import java.text.ParsePosition;
 import java.text.SimpleDateFormat;
 import java.util.Date;
@@ -124,13 +125,20 @@ public class StringUtils {
         }
     }
 
-    static String formatDecimal(double value) {
+    private static String formatDecimal(double value) {
         return StringUtils.formatDecimal(value, 2);
     }
 
+    /**
+     * Format a decimal number while removing trailing zeros of the decimal part (if present).
+     */
     static String formatDecimal(double value, int decimalPlaces) {
-        String result = String.format(Locale.getDefault(), "%1$,." + decimalPlaces + "f", value);
-        return result.replaceAll("[0]*$", "").replaceAll("\\.$", "");
+        if (decimalPlaces < 1) {
+            return Long.toString(Math.round(value));
+        }
+
+        String format = "#." + new String(new char[decimalPlaces]).replace("\0", "#");
+        return new DecimalFormat(format).format(value);
     }
 
     /**