How to use java lower-bound wildcards
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Description
1. Lower-bound wildcards restrict unknown types to specific types or supertypes.
2. Lower-bound wildcards use wildcards ('?').
It is followed by the super keyword, followed by its lower limit.
< ？super A >.
3. The class instantiated by the wildcard must be the current class or the superclass of the current class.
When storing data, the data type can only be the current class or a superclass of the current class.
Example
Public static void addNumbers (List
