How to use Java printf to format output

To format a Java float or double with printf, comply with the identical steps to format an integer with the next two addendums:

1. The conversion specifier for a floating level quantity is %f, not %d.
2. Use the precision parameter to truncate decimals.

Right here is an easy instance of how one can use Java printf to format floats and double output:

bundle com.mcnz.printf.instance;

public class FloatingPointPrintfExample 
  /* Format float and double output with printf. */
  public static void primary(String[] args) 
    double prime    = 1234.12345;
    float  backside = 1234.12345f;
    System.out.printf("%+,.3f :: %,.5f", prime, backside);
    /* Instance prints: +1,234.123 :: 1234.12345 */
  

The %+,.3f setting breaks down like this:

• The plus image + instructs Java printf to incorporate a plus signal if the double is constructive.
• The comma instructs Java printf so as to add a thousandths group separator.
• The .3 instructs Java printf to restrict output to 3 decimal locations.
• %f is the specifier used to format double and floats with printf.

Scientific notation in Java with printf

To output a floating level quantity utilizing scientific notation, merely use %e as an alternative of %f to specify the variables.

bundle com.mcnz.scientific.notation;

public class PrintfScientificNotationExample 
  /* Format float and double output with printf. */
  public static void primary(String[] args) 
    double prime    = 1234.12345;
    float  backside = 1234.12345f;
    System.out.printf("%+,.3e :: %,.5e", prime, backside);
    /* Instance prints: +1.234e+03 :: 1.23412e+03 */
  

Discover how this instance prints out +1.234e+03 :: 1.23412e+03 moderately than +1,234.123 :: 1234.12345, which is what the previous instance generates.

FormatFlagsConversionMismatchException

You should definitely take away any commas within the specifier, as making an attempt so as to add thousandths groupings for scientific notation will lead to a FormatFlagsConversionMismatchException.

Superior double formatting with printf in Java

The next picture demonstrates using varied flags, precision settings and width specifiers to create a desk containing advance formatting of doubles with printf.

Right here’s the code and output of a desk of Java double printf examples.

How do you format a Java char or boolean with printf?

In Java, a char makes use of the %c specifier. A boolean values makes use of %b.

For those who use %C or %B is used to format a boolean or char with Java printf, the values are printed in uppercase.

bundle com.mcnz.scientific.notation;

public class PrintfCharBooleanExample 
  /* Boolean char Java printf instance. */
  public static void primary(String[] args) 
    boolean flag = false;
    char coal = 1234.12345f;
    System.out.printf("%B :: %c :: %C", flag, coal, 'u0077');
    /* Instance prints: FALSE :: a :: W */
  

As you’ll be able to see on this instance, the printf assertion not solely codecs char variables, but it surely additionally converts and correctly prints out unicode character numbers.