0

这可能与 eclipse 的问题有关,但这可能是我的代码某处的问题。无论如何,我有一个 MyLinkedList 类,并且我使用了一个迭代器。当我编写迭代器时,它不允许我通过使用 MyLinkedList.list.add(x, index) 来使用 add 方法。它告诉我:“MyLinkedList 类型中的方法 add(T, int) 不适用于参数 (T, int)”。建议的修复根本不改变任何代码(比如想要将方法的参数类型从 (T, int) 更改为 (T, int)。remove 方法调用相同类型的参数并且工作正常。我会将代码发布到 MyLinkedList 中的 add 方法和迭代器中的 add 方法。

班上:

public void add(T x, int index)
{
    if((index < 0) || (index > size))
        throw new IndexOutOfBoundsException();
    if(size == 0)
    {
        this.head = this.tail = new Node(x, null, null);
    }
    else if(index == 0)
    {
        this.head = new Node(x, this.head, null);
        this.head = this.head.getNext().getPrev();
    }
    else if(index == size)
    {
        this.tail = new Node(x, null, this.tail);
    }
    else 
    {
        Node<T> temp = new Node(null, null, null);

        temp.setData(x);
        if(index < this.size() / 2)
        {
            temp = this.head;
            for(int i = 0; i < index; i++)
            {
                temp = temp.getNext();
            }
        }
        else
        {
            temp = this.tail;
            for(int i = this.size(); i > index; i--)
            {
                temp = temp.getPrev();
            }
        }

        temp.getNext().setPrev(temp);
        temp.getPrev().setNext(temp);
        temp.setData(x);

    }
    this.size++;
}

迭代器方法:

public void add(T x) 
    {
        if(modCount != expModCount)
            throw new ConcurrentModificationException();

        MyLinkedList.this.add(x, index); //the problem is in this line

        modCount--;
        index++;
    }

整个程序(肯定有一些事情不完全正确,但我更关注 add 方法的问题。如果您发现代码有任何其他问题并希望指出我正确的方向,这对我也有帮助):

public class MyLinkedList<T> extends AbstractList<T> 
{

  private static class Node<T>
  {
    private T data;
    private Node<T> prev;
    private Node<T> next;

    /**
     * Constructor
     * @param nodeData - the data in type T that is stored in the node
     * @param nodePrev - the node previous to the node initialized
     * @param nodeNext - the node following the initialized node
     */
    public Node(T nodeData, Node<T> nodePrev, Node<T> nodeNext)
    {
        this.data = nodeData;
        this.prev = nodePrev;
        this.next = nodeNext;
    }

    /**
     * gets the node previous to this one
     * @return returns the node previous to this
     */
    public Node<T> getPrev()
    {
        return this.prev;
    }

    /**
     * sets the node previous to this
     * @param temp the node used to set the previous node to
     */
    public void setPrev(Node<T> temp)
    {
        this.prev = temp.prev;
    }

    /**
     * gets the node after this node
     * @return the node following this node
     */
    public Node<T> getNext()
    {
        return this.next;
    }

    /**
     * sets the node after this node in the list
     * @param prev - the node 
     */
    public void setNext(Node<T> prev)
    {
        this.next = prev.next;
    }

    /**
     * get the data from this node
     * @return the data from this node
     */
    public T getData()
    {
        return this.data;
    }

    /**
     * set the data in this node
     * @param data - the data to be put in this node
     */
    public void setData(T data)
    {
        this.data = data;
    }
}

private int size;
private int modCount;
public Node<T> head;
public Node<T> tail;

/**
 * Constructor for MyLinkedList that sets the head and tail of the list to point to null and the size set to 0
 */
MyLinkedList()
{
    this.head = new Node<T>(null, null, null);
    this.tail = new Node<T>(null, null, null);
    this.size = 0;
}


/**
 * gets the data from the node specified by the index
 * @param index - the index of the node
 * @return the data of the node with index index
 */
@Override
public T get(int index)
{
    Node<T> temp = new Node(null, null, null);

    if((index < 0) || (index > size))
    {
        throw new IndexOutOfBoundsException();
    }

    if(index < this.size() / 2)
    {
        temp = this.head;
        for(int i = 0; i < index; i++)
        {
            temp = temp.getNext();
        }

        return temp.getData();
    }
    else
    {
        temp = this.tail;
        for(int i = this.size(); i > index; i--)
        {
            temp = temp.getPrev();
        }

        return temp.getData();
    }
}

/**
 * adds data to the list at the specified index
 * @param x - the data to be stored
 * @param index - where in the list the data is stored
 */
public void add(T x, int index)
{
    if((index < 0) || (index > size))
        throw new IndexOutOfBoundsException();
    if(size == 0)
    {
        this.head = this.tail = new Node(x, null, null);
    }
    else if(index == 0)
    {
        this.head = new Node(x, this.head, null);
        this.head = this.head.getNext().getPrev();
    }
    else if(index == size)
    {
        this.tail = new Node(x, null, this.tail);
    }
    else 
    {
        Node<T> temp = new Node(null, null, null);

        temp.setData(x);
        if(index < this.size() / 2)
        {
            temp = this.head;
            for(int i = 0; i < index; i++)
            {
                temp = temp.getNext();
            }
        }
        else
        {
            temp = this.tail;
            for(int i = this.size(); i > index; i--)
            {
                temp = temp.getPrev();
            }
        }

        temp.getNext().setPrev(temp);
        temp.getPrev().setNext(temp);
        temp.setData(x);

    }
    this.size++;
}

/**
 * gets the size of the list
 * @return the size of the list
 */
@Override
public int size() 
{
    return this.size;
}

/**
 * @return returns whether or not the list is empty
 */
public boolean isEmpty()
{
    return (this.size() == 0);
}

/**
 * clears the list by setting the head and tail of the list equal to null and the size equal to 0
 */
public void clear()
{
    this.head = new Node<T>(null,null,null);
    this.tail = new Node<T>(null,null,null);

    this.tail = this.head.getNext();
    this.size = 0;
}

/**
 * removes a node from the list
 * @return the data from the removed node
 */
public T remove(int index)
{
    Node<T> temp;
    if ((index < 0) || (index >= size) || isEmpty())
    {
        throw new IndexOutOfBoundsException();
    }
    if(index == 0)
    {
        temp = new Node(this.head.getData(), null, this.head.getNext());
        this.head = this.head.getNext();
    }
    else
    {
        Node<T> prev = new Node(null,null,null);
        prev = getNth(index - 1);
        temp = new Node(prev.getNext().getData(), null, null);
    }
    this.size--;
    return temp.getData();
}

/**
 * gets the node at the index index
 * @param index - the index of the node we want to return
 * @return the node at the specified index
 */
private Node<T> getNth(int index)
{
    Node<T> temp;
    if(index < 0 || index > size)
        throw new IndexOutOfBoundsException();

    if(index < this.size() / 2)
    {
        temp = this.head;
        for(int i = 0; i < index; i++)
        {
            temp = temp.getNext();
        }
    }
    else
    {
        temp = this.tail;
        for(int i = this.size(); i > index; i--)
        {
            temp = temp.getPrev();
        }
    }
    return temp;
}

private class Iterator<T> implements ListIterator<T>
{
    private Node<T> currentNode;
    private int expModCount = modCount;
    int index = 0;

    /**
     * adds the data to the list using the add method from MyLinkedList
     */
    @Override
    public void add(T x) 
    {
        if(modCount != expModCount)
            throw new ConcurrentModificationException();

        MyLinkedList.this.add(x, index);

        modCount--;
        index++;
    }

    /**
     * @return returns true if the current node is not the tail, returns false if the current node is the tail of the list
     */
    @Override
    public boolean hasNext() 
    {
        if (currentNode.equals(MyLinkedList.this.tail))
            return false;
        else
            return true;
    }

    /**
     * @return returns true if the current node is not the head of the list, returns false if the current node is the head of the list
     */
    @Override
    public boolean hasPrevious()
    {
        if (currentNode.equals(MyLinkedList.this.head))
            return false;
        else
            return true;
    }

    /**
     * @return the data from the next node
     */
    @Override
    public T next() 
    {
        if(modCount != expModCount)
            throw new ConcurrentModificationException();
        if(hasNext() == false)
            throw new NoSuchElementException();

        T nextData = currentNode.getData();
        currentNode.setData(currentNode.getNext().getData());

        index++;

        return nextData;
    }

    /**
     * @return the index of the next node
     */
    @Override
    public int nextIndex()
    {
        return index + 1;
    }

    /**
     * @return the data from the previous node
     */
    @Override
    public T previous() 
    {
        if(modCount != expModCount)
        {
            throw new ConcurrentModificationException();
        }
        if(hasPrevious() == false)
        {
            throw new NoSuchElementException();
        }

        T prevData = currentNode.getPrev().getData();
        currentNode.setData(currentNode.getPrev().getData());

        index--;

        return prevData;
    }

    /**
     * @return the index of the previous node
     */
    @Override
    public int previousIndex() 
    {
        return index - 1;
    }

    /**
     * removes a node using the MyLinkedList remove method
     */
    @Override
    public void remove()
    {
        if(modCount != expModCount)
            throw new ConcurrentModificationException();

        MyLinkedList.this.remove(currentNode);
        modCount--;
    }

    /**
     * sets the data of the current node
     * @param x - the data to set to the current node.
     */
    @Override
    public void set(T x) 
    {
        currentNode.setData(x);
    }

}
}
4

2 回答 2

0

嘿,问题是您的 Iterator 接口中的类型 E 和类型 E MyLinkedList 类正在发生冲突。如果您删除 Iterator 的类型 E,则不会出现此问题。但是,为了确保类型安全,请考虑像实现集合框架一样实现它,例如AbstractList.java

于 2012-10-07T02:42:38.950 回答
0

我认为解决此问题的最简单方法是使您的迭代器不是参数化类,而是使用外部类中的参数:

private class MyIterator implements ListIterator<T>

你设置它的方式,<T>inIterator<T>是在屏蔽 in MyLinkedList<T>,所以编译器无法知道它们是否是同一类型。无论如何,内部类都从外部类继承参数,因此您T的迭代器内部类中仍然有一个可用的参数。

顺便说一句,同样的推理也适用于你的Node班级。您应该从类声明中删除参数。您仍然可以在类主体中使用它,因为它是从外部类继承的。

于 2012-10-07T02:55:37.200 回答