Losing magic numbers in Java printf format specifiers to generate columns

Question

In C, the printf function has a great wildcard feature, where you can use an asterisk where you would normally place an int that specifies minimum column width. So you can go

#DEFINE COL_WIDTH 20;

up in the preprocessor directives, and then later you can put

printf("%*s", COL_WIDTH, myString);

to print myString in a 20 character column.

This asterisk trick doesn't seem to be implemented in Java. I have to go

printf("%20s", myString);

instead. This is a flagrant magic number, especially if you are trying to use printf to do something like build a table where you want an easy way to change the column width on a lot of lines at once. So,

is there something I'm missing about printf in Java that makes what I want to do possible, or
is there a neat and more Java-like way of formatting text for output in a table without using magic numbers?

Check this out: http://stackoverflow.com/questions/2550123/java-printf-using-variable-field-size — Balduz, Jan 23 '14 at 16:33
Genius! Thanks Balduz and Marko. THe trick is to build the format string with variables. — mander Don't reinstate Monica, Jan 23 '14 at 16:40
`String myFormatString = "%" + COL_WIDTH + "s"; printf (myFormatString, myString);` — mander Don't reinstate Monica, Jan 23 '14 at 16:41

score 0 · Accepted Answer · answered Jan 23 '14 at 16:39

0

printf("%"+COL_WIDTH+"s", myString);

answered Jan 23 '14 at 16:39

WOUNDEDStevenJones

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Thanks Steven! I'll use this in C too; it will make printf statements a lot more readable if I'm not feeding them column width constants in the arguments list. – mander Don't reinstate Monica Jan 23 '14 at 16:56
anybody care to say why this was downvoted...? – WOUNDEDStevenJones May 25 '15 at 00:36

Losing magic numbers in Java printf format specifiers to generate columns

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