Why can't I add the parent class in the wildcard container?

public class User {

}
public class Child extends User {

}

import java.util.LinkedList;

public class Test {
    public static void main(String[] args) {
        LinkedList<? super Child> linkedList = new LinkedList<>();
        linkedList.add(new Child());
        linkedList.add(new User());
      /**
         * User
         * The method add(capture-sharp2-of ? super Child) in the type LinkedList<capture-sharp2-of ? super Child> is not applicable for the arguments (User)
         */
    }
}
Mar.16,2021

? super Child:ChildChildChildadd

can only be a subclass of add Child or Child, because a subclass of Child must also be of Child type.

MySQL Query : SELECT * FROM `codeshelper`.`v9_news` WHERE status=99 AND catid='6' ORDER BY rand() LIMIT 5
MySQL Error : Disk full (/tmp/#sql-temptable-64f5-1b39cad-2c1b6.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1b39cad-2c1b6.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
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