Why use int over double?

Question

i am using the book beginning java 2. and there is a example showing how the math class works
the program calculates the radius of a circle in feet and inches given that the area is 100 square feet:
public class MathCalc
public static void main(String[]args)
double radius = 0.0;
double circlearea= 0.0;
int feet = 0;
int inches = 0;
radius = Math.sqrt(circleArea/Math.PI);
feet = (int)Math.floor(radius);
inches = (int)Math.round (12.0 * (radius-feet));
System.out.println( Feet + "feet" + inches + "inches");
the output will be 5 feet 8 inches.
my question is why bother with using 'int', why not simply use 'double' for all your variables?
in feet and inches 'int' has been used as the result would have been a floating value. so casting as been used. But doesnt that complicate things?cant one just use long for all variables and forgot about worrying whether the value will fit or not.
thanks
Ali

Answer 1

i am using the book beginning java 2. and there is a
example showing how the math class works
the program calculates the radius of a circle in feet
and inches given that the area is 100 square feet:
public class MathCalc
public static void main(String[]args)
double radius = 0.0;
double circlearea= 0.0;
int feet = 0;
int inches = 0;
radius = Math.sqrt(circleArea/Math.PI);
feet = (int)Math.floor(radius);
inches = (int)Math.round (12.0 *
d (12.0 * (radius-feet));
System.out.println( Feet + "feet" + inches +
"inches");
the output will be 5 feet 8 inches.
my question is why bother with using 'int', why not
simply use 'double' for all your variables?There are several reasons to use int (when appropriate) rather than double. More generally, there are several reasons to use integer arithmetic instead of floating point.
First, integer arithmetic is precise whereas floating point arithmetic is always subject to imprecision. E.g. 6 / 2 always equals 3, 6.0 / 2.0 may equal something like 3.000000000000001.
Second, (related to the above) the results of integer arithmetic operations will not vary from one machine to the next. The results of the same floating point operation may vary from one machine to the next.
Third, integer arithmetic is always faster than floating point.
>
in feet and inches 'int' has been used as the result
would have been a floating value. so casting as been
used. But doesnt that complicate things?The results are cast back to an int because it would look silly and meaningless to print a result of, for instance, 5.00000001 feet, 8.00045 inches.
cant one just
use long for all variables and forgot about worrying
whether the value will fit or not. No. You should never disregard whether the results of arithmetic operations will overflow the size of the word you are using. Even though a long type can contain a pretty huge number, you can still easily overflow it and get nonsensical results.
Also, a 32 bit word is the native size for most of the machines most of us use. This means that arithmetic operations are fastest on int types (for most of us). This shouldn't be a primary design consideration but it should be taken into account.