Java syntax <?> explanation

Question

Hi I came across a code in documentation of android in Grid view for the following code.

gridview.setOnItemClickListener(new OnItemClickListener() {
        publ         


        

Answer 1

The < ? > is a wild card for the generic type, meaning the generic type for AdapterView can be anything at all.

More specifically in this case the parameter on the method may receive an AdapterView with absolutely any generic type. As a note if you wanted to limit the generic type you could do:

AdapterView

This limits the generic type to myClass or anything that extends myClass.

Just as a note:

 AdapterView  and AdapterView 

Are identical.

You can find additional information here in the wildcards section

Java generics documentation