Why does this simple example output such result?

Question

for example:
public class ArithmeticDemo {
public static void main(String[] args){
double x = 27.475;
double y = 7.22;
System.out.println("Subtracting...");
System.out.println(" x - y = " + (x - y));
above example output below:
Subtracting...
x - y = 20.255000000000003
it should output below result:
Subtracting...
x - y = 20.255
who can tell me why?
who can help me?
thanks

Answer 1

hi
im not precise, but the reason for above result should be internal representation of double.
there is something called precision when dealing with floats and double.
if u really bothered about only three digit precision try this!
DecimalFormat df = new DecimalFormat(".000");
System.out.println(" x - y = " + df.format((x - y)));
as my all time favorite author, Kathy sierra used to say,
if u really want to fall asleep try reading how doubles are represented in system, and how they are manipulated.
anyway, if u find anything regarding this please lets all know.
thanks & regards
vijay