Generics for java primitive wrappers

Question

Possible Duplicate:
Comparing the values of two generic Numbers

I want to write some methods for testing Numbers (Long, Integer, etc) like this:

public static <T extends Number> boolean isBetween(T min, T max, T number) {
    return min.compareTo(number) <= 0 && max.compareTo(number) >= 0; 
}

But I'm getting a compile error saying:

The method compareTo(T) is undefined for the type T

How can I fix this?

See http://stackoverflow.com/questions/480632/why-doesnt-java-lang-number-implement-comparable — jam40jeff, Dec 29 '12 at 19:02
See http://stackoverflow.com/questions/2683202/comparing-the-values-of-two-generic-numbers?lq=1 — Frank, Dec 29 '12 at 19:04

score 3 · Accepted Answer · edited May 23 '17 at 12:22

3

Number doesn't implement Comparable (see Why doesn't java.lang.Number implement Comparable? for the rationale), but you can restrict yourself to the Numbers that do:

public static <T extends Number & Comparable<T>> boolean isBetween ...

edited May 23 '17 at 12:22

Community

answered Dec 29 '12 at 19:09

John Dvorak

Don't like the question? :) (btw this 30 question hat is really demeaning) – Bohemian Dec 29 '12 at 19:11
@Bohemian I hunt for the "answer" ones ;-) – John Dvorak Dec 29 '12 at 19:13

score 0 · Answer 2 · answered Dec 29 '12 at 19:16

0

You need to do the casting. the following should work

return ((Comparable<T>) min).compareTo(number) <= 0 && ((Comparable<T>) max).compareTo(number) >= 0;

answered Dec 29 '12 at 19:16

Risin

2 Answers2