Formatted Output

Last modified Wednesday, 28-Feb-2024 13:33:22 UTC.

System.out.printf
- Inherits formated output control from C
- System.out.printf(<format string>,<values>)
- The <format string> contains fixed text and format specifiers
- Format specifiers start with a %
- Example: ArrayCalendar.java
Example: Printf.java
The format specifiers for general, character, and numeric types have the following syntax:
%<flags><width><.precision><conversion>
- Flags (in any order)
  - - = left justification.
  - + = always print with a sign (otherwise only - is printed).
  - space = if first character is not a sign, then a space is printed instead. Only one of + or space can be specified.
  - 0 = in numeric output, specifies padding with 0.
- Width and precision
  - number = minimum field width. A greater width is used if necessary, padded otherwise.
  - precision = maximum number of characters to be printed from a string, or the number of decimal places for float and double, or the minimum number of digits for an integer.
- A width or precision may be specified by *, which takes its value from the next argument.
- The conversion characters are :
  - b for booleans
  - d for integers in decimal
  - o for integers in octal
  - x for integers in hexidecimal
  - c for characters
  - s for anything as a string (like plain print)
  - e for real scientific
  - f for real decimal
  - g is a combination of f and e
  - % for a %.
- There is more information in the Java documentation
Formatted strings
- The String class provides a way to create strings using printf style formatting.
- Example: FormatString.java

Exercises

What printf format specifier is good for money values?

Exam Style Questions

What is the exact output from the following (use an upsidedown triangle to indicate a space in the output):

int birthday = 27;
double catch22 = 22.22;
long fibonacciLimit = 95;

System.out.printf("%-8.0f %%%+d\n%5d\n",catch22,birthday,fibonacciLimit);