Q:

Cannot output formatted double in Java

Here's what I do:
double x = 7.0;  
System.out.printf("%.2f", x);

Eclipse gives me this error "The method printf(String, Object[]) in the type PrintStream is not applicable for the arguments (String, double)"

A:

Are you using a version of Java older than 1.5? Or maybe an older compiler compliance setting in Eclipse? (e.g. 1.4) In fact, I am pretty sure that is the cause - I just switched my compliance setting to 1.4 and I get the same error as you.
Check your Project's Compiler Compliance setting:

Select the Project
Right click and choose Properties
go to 'Java Compiler'
change your compiler compliance and ensure you are using a JRE of that version or higher

This will work once you are using Java 1.5 or higher, since the printf method was added in 1.5.

