如何将对象添加到链接列表中？

Question

我一直在从事一个项目，我必须实现一个java类来实现双向链表的使用。我已经完成了 LinkedList 类的所有方法。我只是不确定如何实际将节点对象添加到列表中。这是到目前为止我的代码，测试在底部。任何帮助，将不胜感激。谢谢

public class LinkedList {

    private Node first;
    private Node current;
    private Node last;
    private int currentIndex;
    private int numElements;

    public LinkedList() {
        this.first = null;
        this.last = null;
        this.numElements = 0;
        this.current = null;
        this.currentIndex = -1;
    }

    private class Node {

        Node next;
        Node previous;
        Object data;
    }

    public boolean hasNext() {
        return (current != null && current.next != null);
    }

    public Object next() {
        if (!this.hasNext()) {
            throw new IllegalStateException("No next");
        }

        current = current.next;
        return current.data;

    }

    public boolean hasPrevious() {
        return (current != null && current.previous != null);

    }

    public Object previous() {
        if (!this.hasPrevious()) {
            throw new IllegalStateException("No previous");
        }
        current = current.previous;
        return current.data;

    }

   int nextIndex() {
        int index = numElements;
        if (hasNext()) {
            index = this.currentIndex + 1;
        }
        System.out.println(index + "The current index is " + current);
        return index;
    }

    int previousIndex() {
        int index = -1;
        if (hasPrevious()) {
            index = this.currentIndex - 1;
        }
        System.out.println(index + "The current index is " + current);
        return index;
    }

    public void set(Object o) {
        if (this.current == null) {
            throw new IllegalStateException("No node found, cannot set.");
        }
        current.data = o;
    }

    public int size() {
        return numElements;
    }

    public void add(Object o) {       
        Node newNode = new Node();
        newNode.data = o;
        if (first == null) {
            first = newNode;
            last = newNode;
            newNode.next = null;

        } else if (first != null) {
            if (current == null) {
                newNode.previous = null;
                newNode.next = first;
                first.previous = newNode;
                first = newNode;
            } else if (current == last) {
                newNode.previous = current;
                newNode.next = null;
                current.next = newNode;
                last = newNode;
            } else {
                newNode.previous = current;
                newNode.next = current.next;
                current.next.previous = newNode;
                current.next = newNode;
            }
        }
        current = newNode;
        numElements++;
        currentIndex++;

    }

    public void remove() {
        if (current != null) {
            if (current == first && current == last) {
                first = null;
                last = null;
            } else if (current == last) {
                current.previous = null;
                last = current.previous;
            } else if (current == last) {
                current.previous.next = null;
                last = current.previous;
            } else {
                current.previous.next = current.next;
                current.next.previous = current.previous;
            }
            current = current.next;
            numElements--;
        }
    }
}



import java.util.Scanner;


public class LinkedListTest {
    public static void main(String[] args) {
        Scanner keyboard = new Scanner(System.in);
        String name;
        int index;

        LinkedList<Object> listOne = new LinkedList<Object>();

        listOne.add(object o);

    }
}

Answer 1

发布的类 LinkedList 对我来说看起来很实用。

确保您的测试代码不会混淆此类和java.util.LinkedListJava 为您提供的类（它是现有 Collections 框架的一部分）。

为了清楚起见，我建议将您的班级重命名为类似的名称MyLinkedList

以下代码有效，输出为“0”，“2”：

public class MyLinkedListTest {

    public static final void main(String[] args) {

        MyLinkedList list = new MyLinkedList();
        System.out.println("Number of items in the list: " + list.size());

        String item1 = "foo";
        String item2 = "bar";

        list.add(item1);
        list.add(item2);

        System.out.println("Number of items in the list: " + list.size());      

        // and so on...
    }

}