Re: Generics: how to read actual type parameters

marek.dudek@xxxxxxxxx wrote:
For example:

public class Pair<S> {
public String toString() {
Class clas = ??? ;
return "Pair of " + clas.toString();
}
public S first;
public S second;
}

1. Don't use tabs in Usenet posts.
2. What you are probably intending to do is impossible as specified. There is no possible way at runtime to get the class of S. Java erases the types of the parameters at runtime.
3. Class is generic. Use Class<?> instead.

The easiest thing you can do is:
Class<?> clas = first.getClass();

A potentially tighter bound is:
Class<?> left = first.getClass();
Class<?> right = second.getClass();
Class<?> clas = left;

while (!clas.isAssignableFrom(right))
clas = clas.getSuperclass();

(This returns the last common ancestor of the classes of first and second)
--
Beware of bugs in the above code; I have only proved it correct, not tried it. -- Donald E. Knuth
.

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