Java Generics E extends Comparable 留下警告

Question

我正在尝试创建一个通用类，其中 E extends Comparable E 但我在 Eclipse 中收到一条警告:

LinkedList.Node is a raw type. References to generic type LinkedList E .Node E should be parameterized

代码如下:

public class LinkedList<E extends Comparable<E>>



{
    // reference to the head node.
    private Node head;
    private int listCount;

    // LinkedList constructor
 public void add(E data)
    // post: appends the specified element to the end of this list.
    {
        Node temp = new Node(data);
        Node current = head;
        // starting at the head node, crawl to the end of the list
        while(current.getNext() != null)
        {
            current = current.getNext();
        }
        // the last node's "next" reference set to our new node
        current.setNext(temp);
        listCount++;// increment the number of elements variable
    }
 private class Node<E extends Comparable<E>>
    {
        // reference to the next node in the chain,
        Node next;
        // data carried by this node.
        // could be of any type you need.
        E data;


        // Node constructor
        public Node(E _data)
        {
            next = null;
            data = _data;
        }

        // another Node constructor if we want to
        // specify the node to point to.
        public Node(E _data, Node _next)
        {
            next = _next;
            data = _data;
        }

        // these methods should be self-explanatory
        public E getData()
        {
            return data;
        }

        public void setData(E _data)
        {
            data = _data;
        }

        public Node getNext()
        {
            return next;
        }

        public void setNext(Node _next)
        {
            next = _next;
        }
    }


}

Answer 1

这里的主要问题是通用 <E>在 Node 中隐藏了 E来自 LinkedList<E extends Comparable<E>> .此警告应出现在此处:

private class Node<E extends Comparable<E>> {
                   ^ here you should get a warning with the message
                   The type parameter E is hiding the type E
}

自 Node是一个内部类，它可以直接访问泛型 E在 LinkedList 中声明.这意味着，您可以轻松声明 Node没有通用类型的类:

private class Node {
    E data;
    Node next;
    //rest of code...
}

然后你可以轻松使用Node node类中的变量。

---

请注意，如果您声明 Node作为静态类，那么泛型是必需的，那么你不应该声明原始变量。这将是:

private static Node<E extends Comparable<E>> {
    E data;
    Node<E> next;
    //rest of code...
}

private Node<E> head;

哪里E用于 static class Node不同于 E在 LinkedList 中声明的通用.