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What does List<?> mean, does it mean simply a list of objects of unspecified type?
Googling for the string <?> returns nothing useful (:
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In Java, a list interface is an ordered collection of objects in which duplicate values can be stored. Since a List preserves the insertion order, it allows positional access and insertion of elements. List interface is implemented by the following classes: ArrayList. LinkedList.
List in Java provides the facility to maintain the ordered collection. It contains the index-based methods to insert, update, delete and search the elements. It can have the duplicate elements also. We can also store the null elements in the list.
In practical terms there is no difference, they both compile down to the exact same code. List<Object> though is showing that you have thought about what will go in the list and know it could be anything, whereas List on its own shows nothing.
super T denotes an unknown type that is a supertype of T (or T itself; remember that the supertype relation is reflexive). It is the dual of the bounded wildcards we've been using, where we use ? extends T to denote an unknown type that is a subtype of T .
As Tom said, the ?, or unbounded wildcard, means that the type of the object is not specified. It could be unknown, could be meant for multiple possible values or might be just plain irrelevant. Your example, List<?>, is pronounced "List of unknown." It's convenient because it's flexible, but there are also some pitfalls because you can't shove random objects in and pull them out of groups of unknown with total impunity.
Resources:
Incidentally, your Google search failed because Google doesn't truck with special characters:
With some exceptions, punctuation is ignored (that is, you can't search for @#$%^&*()=+[]\ and other special characters).
-Google help page
(EDIT: I must have been really tired when I wrote this last night. Cleaned up formatting/added a little info.)
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