Im a PHP-programmer and wonder what this line means.
System.out.printf("exp(%.3f) is %.3f%n", x, Math.exp(x))
what does %.3f, %.3f%n and the comma x means?
It is similar to C's printf:
http://java.sun.com/j2se/1.5.0/docs/api/java/util/Formatter.html#syntax
PHP has a similar function: http://php.net/printf The Documentation of the Java version can be found here: http://java.sun.com/javase/6/docs/api/java/util/Formatter.html
The % character is a format specifier which controls how the corresponding variables are formatted.
In this particular case, the two argumnents x and Math.exp(x) are formatted as floats with three fractional digits.
You should of course already know this, even as a PHP coder, since PHP itself appears to have printf and the format specifiers are listed here.
%.3f means the same thing in Java as in C/C++. It means a floating point number with three digits after the decimal point.
This is standard printf formatting. The % stands for 'put an argument here', and the various dots, numbers and letters after the % specify the type of argument.
and, to be complete, the %n represents the platform specific line separator in the printf...
来源：https://stackoverflow.com/questions/2030561/what-does-the-mean-in-java