In comp.lang.java.advocacy, [EMAIL PROTECTED]
<[EMAIL PROTECTED]>
wrote
on 25 Aug 2006 12:05:21 -0700
<[EMAIL PROTECTED]>:
> lets say you want a generic numerical algorithom like sum
>
> Ruby
>
> def sum lst
> lst.inject(0){|total,current| total*current}
> end
>
> Java // i dont know if there is a numeric super class for numbers
>
> class Sum{
> public static int sum(int[] lst){
> int total = 0;
> for(int current : lst){
> total+=current;
> }
> return total;
> }
> // repeat for all other number types
> }
>
There isn't; Java makes the distinction between an int and
an Integer, a double and a Double. Java 5 did introduce
autoboxing, which makes things like
Number[] numbers = new Number[]{1, 2.3, 4, 5.6};
possible, and Number is a baseclass for both Integer and
Double (but not int and double).
Therefore, one could write:
public class Sum {
public static double sum(int[] lst)
{
Number[] nlst = new Number[lst.length];
for(int i = 0; i < nlst.length; i++) nlst[i] = new Integer(lst[i]);
return sum(Arrays.asList(nlst));
}
public static double sum(double[] lst)
{
Number[] nlst = new Number[lst.length];
for(int i = 0; i < nlst.length; i++) nlst[i] = new Double(lst[i]);
return sum(Arrays.asList(nlst));
}
public static double sum(float[] lst)
{
Number[] nlst = new Number[lst.length];
for(int i = 0; i < nlst.length; i++) nlst[i] = new Double(lst[i]);
return sum(Arrays.asList(nlst));
}
public static double sum(Number[] lst)
{
return sum(Arrays.asList(lst));
}
public static double sum(Collection<Number> lst)
{
double sum = 0;
for(Iterator<Number> i = lst.iterator(); i.hasNext())
sum += i.next().doubleValue();
return sum;
}
}
A rather ugly but possibly useful duckling.
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