Java String.format()
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External
- Format String syntax: https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/Formatter.html#syntax
- http://docs.oracle.com/javase/7/docs/api/java/lang/String.html#format%28java.lang.String,%20java.lang.Object...%29
Internal
Overview
Format string:
%[argument_index$][flags][width][.precision]conversion
String
String arg = "blah" String.format("%1$-50s", arg);
This formats the first argument (%1$) as a string "s", to occupy at least 50 characters (width) and it left-justifies it ("-").
For general argument types, the precision is the maximum number of characters to be written to the output.
Parameterized Width
int width=10; String format = "%1$-" + width + "s"; String.format(format, s);
Floating Point
For the floating-point conversions 'e', 'E', and 'f' the precision is the number of digits after the decimal separator. The conversion is done with rounding:
double arg = 77.999 String.format("%1$.2f", arg);
will display "78.00"
Integer
int arg = 77.
String.format("%1$3d", arg);
will display " 77"
Hexadecimal Integer
Display a argument as a 0-padded hexadecimal integer on at least 2 characters. Format string:
int i = 10;
String.format("%1$02x", i);
will display "0a".
The result will be 0-padded (flag
is "0"), will be displayed on two characters and more (width
is 2) and it will be rendered as a hexadecimal (conversion
is "x").