Java does not have any built in equivalent to C's printf/sprintf/fprintf family of functions that specify the width and precision of numbers converted into strings. Since Java does not support variable length argument lists, it's not possible to write exact equivalents for these functions. Instead the approach that must be taken is to convert one number at a time into a string according to a format specification, then write the resulting string onto the appropriate output stream. This is a more flexible solution, but it's far from obvious.

In Java 1.1, the java.text package contains classes that format numbers according to particular needs. In particular it's worth getting to know the java.text.NumberFormat and java.text.DecimalFormat classes, though these can't handle exponential notation. I've begun work on my own formatting class that does handle exponential and other notations available through printf(). It can be found at http://metalab.unc.edu/javafaq/formatter/. Gary Cornell and Cay Horstmann's popular book Core Java also includes such a class. You can probably find more at Gamelan.