[Java] String format() Format Specifiers

From Javadoc : https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/Formatter.html 

 Example :

Suppose we have int x = 123, and we want to pad 0 .

String.format("%1$013d", x);

• The format specifiers for general, character, and numeric types have the following syntax:

     %[argument_index$][flags][width][.precision]conversion
   

  The optional argument_index is a decimal integer indicating the position of the argument in the argument list. The first argument is referenced by "1$", the second by "2$", etc.

  The optional flags is a set of characters that modify the output format. The set of valid flags depends on the conversion.

  The optional width is a positive decimal integer indicating the minimum number of characters to be written to the output.

  The optional precision is a non-negative decimal integer usually used to restrict the number of characters. The specific behavior depends on the conversion.

  The required conversion is a character indicating how the argument should be formatted. The set of valid conversions for a given argument depends on the argument's data type.

• The format specifiers for types which are used to represents dates and times have the following syntax:

     %[argument_index$][flags][width]conversion
   

  The optional argument_index, flags and width are defined as above.

  The required conversion is a two character sequence. The first character is 't' or 'T'. The second character indicates the format to be used. These characters are similar to but not completely identical to those defined by GNU date and POSIX strftime(3c).

• The format specifiers which do not correspond to arguments have the following syntax:

     %[flags][width]conversion
   

  The optional flags and width is defined as above.

  The required conversion is a character indicating content to be inserted in the output.

Format Specifier	Data Type	Output
%a	floating point (except BigDecimal)	Returns Hex output of floating point number.
%b	Any type	"true" if non-null, "false" if null
%c	character	Unicode character
%d	integer (incl. byte, short, int, long, bigint)	Decimal Integer
%e	floating point	decimal number in scientific notation
%f	floating point	decimal number
%g	floating point	decimal number, possibly in scientific notation depending on the precision and value.
%h	any type	Hex String of value from hashCode() method.
%n	none	Platform-specific line separator.
%o	integer (incl. byte, short, int, long, bigint)	Octal number
%s	any type	String value
%t	Date/Time (incl. long, Calendar, Date and TemporalAccessor)	%t is the prefix for Date/Time conversions. More formatting flags are needed after this. See Date/Time conversion below.
%x	integer (incl. byte, short, int, long, bigint)	Hex string.

Source : 

https://www.javatpoint.com/java-string-format

https://stackoverflow.com/questions/5762836/what-does-1-mean-when-used-in-string-format-java

https://www.geeksforgeeks.org/format-specifiers-in-java/