[ Java 常見問題 ] How can I truncate a double to only two decimal places in Java?

Source From Here 
Question 
For example I have the variable 3.545555555, which I would want to truncate to just 3.54. 

How-To 
If you want that for display purposes, use java.text.DecimalFormat: 

groovy:000> import java.text.DecimalFormat
===> java.text.DecimalFormat
groovy:000> dv = 0.123456789
===> 0.123456789
groovy:000> new DecimalFormat("#.##").format(dv)
===> 0.12

If you need it for calculations, use java.lang.Math: 

groovy:000> Math.floor(dv * 100) / 100
===> 0.12

Supplement 
* How to round a number to n decimal places in Java