How do I print a double value without scientific notation using Java?

Question

I want to print a double value in Java without exponential form.

double dexp = 12345678;
System.out.println(\"dexp: \"+dexp);

It shows this

Answer 1

In short:

If you want to get rid of trailing zeros and Locale problems, then you should use:

double myValue = 0.00000021d;

DecimalFormat df = new DecimalFormat("0", DecimalFormatSymbols.getInstance(Locale.ENGLISH));
df.setMaximumFractionDigits(340); // 340 = DecimalFormat.DOUBLE_FRACTION_DIGITS

System.out.println(df.format(myValue)); // Output: 0.00000021

Explanation:

Why other answers did not suit me:

• Double.toString() or System.out.println or FloatingDecimal.toJavaFormatString uses scientific notations if double is less than 10^-3 or greater than or equal to 10^7

• By using %f, the default decimal precision is 6, otherwise you can hardcode it, but it results in extra zeros added if you have fewer decimals. Example:

  double myValue = 0.00000021d;
  String.format("%.12f", myvalue); // Output: 0.000000210000
  

• By using setMaximumFractionDigits(0); or %.0f you remove any decimal precision, which is fine for integers/longs, but not for double:

  double myValue = 0.00000021d;
  System.out.println(String.format("%.0f", myvalue)); // Output: 0
  DecimalFormat df = new DecimalFormat("0");
  System.out.println(df.format(myValue)); // Output: 0
  

• By using DecimalFormat, you are local dependent. In French locale, the decimal separator is a comma, not a point:

  double myValue = 0.00000021d;
  DecimalFormat df = new DecimalFormat("0");
  df.setMaximumFractionDigits(340);
  System.out.println(df.format(myvalue)); // Output: 0,00000021
  

  Using the ENGLISH locale makes sure you get a point for decimal separator, wherever your program will run.

Why using 340 then for setMaximumFractionDigits?

Two reasons:

• setMaximumFractionDigits accepts an integer, but its implementation has a maximum digits allowed of DecimalFormat.DOUBLE_FRACTION_DIGITS which equals 340
• Double.MIN_VALUE = 4.9E-324 so with 340 digits you are sure not to round your double and lose precision.