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# Math.round??

sonir shah
Ranch Hand

Joined: Nov 01, 2001
Posts: 435
public class RoundTest
{
public static void main(String args[])
{
double d = 3.5;
int i = (int) d;
i *= (int) Math.round(d);
i *= (int) Math.round(d-6);
System.out.println(i);
}
}
Options :
1)-24
2)-36
3)-48
4)-18
5) none
I tried running the program , it should -24
Can any body explain me ?>
Sonir
Rob Ross
Bartender

Joined: Jan 07, 2002
Posts: 2205
double d = 3.5;
int i = (int) d;
i *= (int) Math.round(d);
i *= (int) Math.round(d-6);
System.out.println(i);
First, you assign 3.5 to the variable "d". Next, the value in d is cast to an int and stored in the variable i. By casting from a double to an int, you loose the fractional part of the number; it is simply truncated. So i gets the value 3.
Next, the static function round() in the Math class is called with a double argument of value 3.5. This returns the rounded value, which will be 4. (See the JavaDoc for how round() works.) This value (4) is cast to an int, then the "times equal" operator is applied to the operands, and the value 12 is stored in i. (i previously had 3, and we multiplied this by 4).
In the same way, the next line will evaluate to
i*= -2 (d-6 rounds to -2)
Since i currently has 12, 12*-2 = -24, and this is assigned to i.
Rob

Rob
SCJP 1.4
Chun Wong
Greenhorn

Joined: Jan 11, 2002
Posts: 3
Hi, all! I am new here. How to use "Code" tag?
Thank you!
Jose Botella
Ranch Hand

Joined: Jul 03, 2001
Posts: 2120
Just push the button that says code an place your code between the tags that appear