I can't see any difference between this default sort method(from java.util.Collections)
public static <T extends Comparable<? super T>> void sort(List<T> list) {
//implementation
}
..and this :
public static <T extends Comparable<T>> void mySort(List<T> list) {
//implementation
}
Although I know about the differences between the 'upper' and 'lower' bounded wildcards,I still don't understand why they use '? super T' instead of simple 'T' in this case.If I use these methods,I get the same result with both of them.Any suggestions?
With your version, the following will not compile:
class Base implements Comparable<Base> { ... }
class Derived extends Base { ... }
List<Derived> list = ...;
mySort(list);
Derived does not extend Comparable<Derived>. However, it does extend Comparable<Base> (and thus, Comparable<? super Derived>).
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