System.out.printf("PI =%5.2f%n", Math.PI);  
System.out.printf("PI =%5.3f%n", Math.PI);  
System.out.printf("PI =%10.1f%n", Math.PI);  

PI = 3.14
PI =3.142
PI =       3.1 

Format Specifiers

public class FloatDemoA
{
  public static void main ( String[] args )
  {
    double first = 12345.6789 ;    
    double second = -45.97 ;  
    System.out.printf( "first = %10.3f;  second = %10.3f;  sum = %f", first, second, first+second  );
  }
}

first =  12345.679;  second =    -45.970;  sum =  12299.708900

Notes:

• Each format specifier matches a value in the arguments.
• The value may be an expression.
• The type of each specifier matches the conversion code of the specifier.
• Ordinary text (like "first = ") is mixed in with the specifiers.
• If the field width is 10, at least 10 characters are output, including spaces.
  • The dot and the minus are part of the width.
  • Numbers are right-justified by default.
• A precision of 3 asks for 3 digits to the right of the decimal point.
  • Sometimes this calls for rounding.
  • Sometimes zeros are appended.
• If only the conversion code is used (%f), you get the default format.

double value = 123456.120001;
System.out.printf("value =%5.2f", value);