Formatting a Double to a String for Swing output

Question

Hi, I'm new to Java and I'm working on a project with AWT & Swing. I'm trying to read in a user entered number, convert it to a double, work on it and then output the String value of the result with only two decimal places. The code I have is:
public void actionPerformed(ActionEvent e)
double result = 99;
double temp;
DecimalFormat newTemp = new DecimalFormat("#,###.00");
if (e.getSource() == bConvert1)
temp = (Double.parseDouble(tTemp1.getText().trim()));
result = (temp*1.8)+32;
newTemp.format(result);
tResult1.setText(String.valueOf(result));
else if (e.getSource() == bConvert2)
temp = (Double.parseDouble(tTemp2.getText().trim()));
result = (5.0/9)*(temp-32);
newTemp.format(result);
tResult2.setText(String.valueOf(result));
This is working for some values, but for some values entered, the result displayed is just the remainder.

Answer 1

The reason it doesn't always work could be because DecimalFormat (for reasons known only to Sun) uses ROUND_HALF_EVEN...
This means that you will have to round the value to the number of decimal places you require before calling format()
I use something like the following formatter class
class Formatter {
  public static final int DEFAULT_PRECISION = 2;
  public static final String DEFAULT_PATTERN = "#.00";
  public static final String ZEROS = "0000000000000000";
  public static String convertDoubleToString(Double d) {
    return convertDoubleToString(round(d, DEFAULT_PRECISION), DEFAULT_PATTERN);
  public static String convertDoubleToString(double d) {
    return convertDoubleToString(round(d, DEFAULT_PRECISION), DEFAULT_PATTERN);
  public static String convertDoubleToString(Double d, int precision) {
    return convertDoubleToString(round(d, precision), "#." + ZEROS.substring(precision));
  public static String convertDoubleToString(double d, int precision) {
    return convertDoubleToString(round(d, precision), "#." + ZEROS.substring(precision));
  public static String convertDoubleToString(Double d, String pattern) {
    return new DecimalFormat(pattern).format(d.doubleValue());
  public static String convertDoubleToString(double d, String pattern) {
    return new DecimalFormat(pattern).format(d);
  private static final double round(Double d, int precision) {
    double factor = Math.pow(10, precision);
    return Math.round((d.doubleValue() * factor)) / factor;
  private static final double round(double d, int precision) {
    double factor = Math.pow(10, precision);
    return Math.round((d * factor)) / factor;
}