Generic Method declaration

[Anthony Karta]

from john myer's mock test.

I just playing around with the code, and wonder why we can declare method at #1 and #2?? what is the logic?

String is part of <? super String>

    
class test {
    static List<? super String> tester = new ArrayList<String>();
 
    public static void main(String args[]) {
        seth(tester); // 2  Non-static can be referenced from static context
        // #1 - ? extends String can be applied to ? super String
        // #2 - String can be applied to ? super String
    }
 
    //public static <T> void seth(List<? extends String> type) { // #1
    //public static <T> void seth(List<String> type) { // #2
    public static <T> void seth(List<? super String> type) {
        type.add("hi"); // 1
    }
}

[Aniket Patil]

why we can declare method at #1 and #2

we can't!

List<? super String> can take a String or a superclass of String as a type argument. List<String> can have only a String type argument. The compiler cannot be sure that you would always pass in a List<String> since List<? super String> also allows a List<Object>. Hence, disallowed.