[#8557] Standardize locale

src/main/java/teammates/common/util/StringHelper.java

@@ -1,6 +1,7 @@
 package teammates.common.util;
 
 import java.text.DecimalFormat;
+import java.text.DecimalFormatSymbols;
 import java.util.Collections;
 import java.util.List;
 import java.util.Objects;
@@ -179,7 +180,9 @@ public static <T> String toString(List<T> list, String delimiter) {
  * Converts a double value between 0 and 1 to 3dp-string.
  */
  public static String toDecimalFormatString(double doubleVal) {
- DecimalFormat df = new DecimalFormat("0.###");
+ DecimalFormatSymbols syms = new DecimalFormatSymbols();
+ syms.setDecimalSeparator('.');
+ DecimalFormat df = new DecimalFormat("0.###", syms);
  return df.format(doubleVal);
  }
 

src/main/java/teammates/common/util/TimeHelper.java

@@ -7,6 +7,7 @@
 import java.time.ZonedDateTime;
 import java.time.format.DateTimeFormatter;
 import java.time.format.DateTimeParseException;
+import java.util.Locale;
 
 /**
  * A helper class to hold time-related functions (e.g., converting dates to strings etc.).
@@ -105,7 +106,9 @@ public static String formatInstant(Instant instant, String timeZone, String patt
  if (zonedDateTime.getHour() == 12 && zonedDateTime.getMinute() == 0) {
  processedPattern = pattern.replace("a", "'NOON'");
  }
- DateTimeFormatter formatter = DateTimeFormatter.ofPattern(processedPattern);
+ DateTimeFormatter formatter = DateTimeFormatter
+ .ofPattern(processedPattern)
+ .withLocale(Locale.US);
  return zonedDateTime.format(formatter);
  }