Java 泛型约束

import java.util.List;
import java.util.ArrayList;
import java.util.LinkedList;

/**
 * Created by Administrator on 2016/12/30 0030.
 */
public class ListGenericFoo<T extends List>
{
    private T[] fooArray;

    public T[] getFooArray()
    {
        return fooArray;
    }

    public void setFooArray(T[] fooArray)
    {
        this.fooArray = fooArray;
    }

    public static void main(String[] args)
    {
        ListGenericFoo<LinkedList> foo1 = new ListGenericFoo<LinkedList>();
        ListGenericFoo<ArrayList> foo2 = new ListGenericFoo<ArrayList>();

        LinkedList[] linkedLists = new LinkedList[10];
        foo1.setFooArray(linkedLists);

        ArrayList[] arrayLists = new ArrayList[10];
        foo2.setFooArray(arrayLists);

    }
}

  ArrayList<? extends List> list=null;
         list=new ArrayList<LinkedList>();
         list=new ArrayList<ArrayList>();

    ArrayList<? super ArrayList> list=null;
         list=new ArrayList<Object>();
         list=new ArrayList<ArrayList>();