链表的迭代器

Question

我的项目应该实现两个 classes。一个基本链表和一个排序链表。一切似乎都工作正常，除了由于某种原因我无法遍历排序的链表。 class结构如下：

public class BasicLinkedList<T> implements Iterable<T> {
    public int size;

    private class Node {
        private T data;
        private Node next;

        private Node(T data) {
            this.data = data;
            next = null;
        }
    }

    private Node head;
    private Node tail;

    public BasicLinkedList() {
        head = tail = null;
    }
//Add, remove method 

public Iterator<T> iterator() {
        return new Iterator<T>() {

            Node current = head;

            @Override
            public boolean hasNext() {
                return current != null;
            }

            @Override
            public T next() {
                if(hasNext()){
                    T data = current.data;
                    current = current.next;
                    return data;
                }
                return null;
            }

            @Override
            public void remove(){
                throw new UnsupportedOperationException("Remove not implemented.");
            }

        };

现在，当我测试这个 class 时，它工作得很好。迭代器工作，我可以测试它。问题出在扩展这个链表的排序链表 class 中。这是它的实现和我在构造函数中使用的比较器 class：

public class SortedLinkedList<T> extends BasicLinkedList<T>{
    private class Node{
        private T data;
        private Node next;

        private Node(T data){
            this.data = data;
            next = null;
        }
    }

    private Node head;
    private Node tail;
    private Comparator<T> comp;

    public SortedLinkedList(Comparator<T> comparator){
        super();
        this.comp = comparator;
    }

这里是比较器 class 和测试 I 运行在单独的 class:

public class intComparator implements Comparator<Integer>{
        @Override
        public int compare(Integer o1, Integer o2) {
            return o1 - o2;
        }
}

public static void main(String[] args) {
System.out.println("---------------SortedLinkedList--------------");
        SortedLinkedList<Integer> sortedList = new SortedLinkedList<Integer>(new intComparator());
        sortedList.add(3);
        sortedList.add(5);
        sortedList.add(2);
        for(int i: sortedList){
            System.out.println(i);
        }
    }

没有打印出来。我假设继承的迭代器会帮助我遍历这个没有问题并且显然它是合法的，因为 for-each 循环编译。只是没有打印出来。我调试了它，所有添加、删除的东西都按预期工作。只是迭代器没有做它应该做的事。我应该为此 class 创建一个单独的新迭代器吗？但那不是多余的代码吗，因为我已经继承了它？感谢帮助！

编辑：这是排序列表的添加方法

public SortedLinkedList<T> add(T element){
        Node n = new Node(element);
        Node prev = null, curr = head;
        if(head == null){
            head = n;
            tail = n;
        }
        //See if the element goes at the very front
        else if(comp.compare(n.data, curr.data) <= 0){
            n.next = head;
            head = n;
        }
        //See if the element is to be inserted at the very end
        else if(comp.compare(n.data, tail.data)>=0){
            tail.next = n;
            tail = n;
        }
        //If element is to be inserted in the middle
        else{
            while(comp.compare(n.data, curr.data) > 0){
                prev = curr;
                curr = curr.next;
            }
            prev.next = n;
            n.next = curr;
        }

        size++;
        return this;
    }

Answer 1

1) SortedLinkedList 扩展 BasicLinkedList 但两者都有

private Node head; 
private Node tail

这是错误的。如果你想继承子 class 中的那些字段，你应该在超级 class 中将变量标记为受保护，并将它们从子 class.

中删除

2) private class Node 也是如此。您在 SortedLinkedList 和 BasicLinkedList 中都声明了节点 class。你应该做的是声明一次，（也许在超级class？）并在两个地方使用相同的class。如果这样做，classes 应该可以访问构造函数和字段。所以你将不得不更改访问修饰符（private 是你现在拥有的）。

我将 post 下面的代码有效，但我没有花任何时间在设计上。只是 posting 它来演示如何更改代码以使其工作。您将必须决定使用哪些访问修饰符以及将 classes.

放在哪里

import java.util.Comparator;
import java.util.Iterator;

public class Test {
    public static void main(String[] args) {
        System.out.println("---------------SortedLinkedList--------------");
        SortedLinkedList<Integer> sortedList = new SortedLinkedList<Integer>(new intComparator());
        sortedList.add(3);
        sortedList.add(5);
        sortedList.add(2);
        for (int i : sortedList) {
            System.out.println(i);
        }
    }
}

class BasicLinkedList<T> implements Iterable<T> {
    public int size;

    class Node {
        T data;
        Node next;

        Node(T data) {
            this.data = data;
            next = null;
        }
    }

    protected Node head;
    protected Node tail;

    public BasicLinkedList() {
        head = tail = null;
    }

    // Add, remove method

    public Iterator<T> iterator() {
        return new Iterator<T>() {

            Node current = head;

            @Override
            public boolean hasNext() {
                return current != null;
            }

            @Override
            public T next() {
                if (hasNext()) {
                    T data = current.data;
                    current = current.next;
                    return data;
                }
                return null;
            }

            @Override
            public void remove() {
                throw new UnsupportedOperationException("Remove not implemented.");
            }

        };

    }
}

class SortedLinkedList<T> extends BasicLinkedList<T> {


    private Comparator<T> comp;

    public SortedLinkedList(Comparator<T> comparator) {
        super();
        this.comp = comparator;
    }

    public SortedLinkedList<T> add(T element) {
        Node n = new Node(element);
        Node prev = null, curr = head;
        if (head == null) {
            head = n;
            tail = n;
        }
        // See if the element goes at the very front
        else if (comp.compare(n.data, curr.data) <= 0) {
            n.next = head;
            head = n;
        }
        // See if the element is to be inserted at the very end
        else if (comp.compare(n.data, tail.data) >= 0) {
            tail.next = n;
            tail = n;
        }
        // If element is to be inserted in the middle
        else {
            while (comp.compare(n.data, curr.data) > 0) {
                prev = curr;
                curr = curr.next;
            }
            prev.next = n;
            n.next = curr;
        }

        size++;
        return this;
    }
}

class intComparator implements Comparator<Integer> {
    @Override
    public int compare(Integer o1, Integer o2) {
        return o1 - o2;
    }
}

链表的迭代器

Iterator for a linkedlist

java

iterator

linked-list