链表未初始化

Question

我无法初始化 LinkedList1，我得到的错误是“语法错误，插入“；”来完成 BlockStatements。我知道还有其他方法可以创建一个链表，但我想在其他方法之前先使用这种方法. 任何帮助都会让我成为一个非常感谢的编码员:)

import java.util.*;

public class LinkedList1 {

    private class Node
    {
        String value;
        Node next;

        Node(String val, Node n)
        {
            value=val;
            next=n;
        }

        Node(String val)
        {
            this(val,null);
        }
    }

    private Node first;
    private Node last;

    public LinkedList1()
    {
        first=null;
        last=null;
    }

    public boolean isEmpty()
    {
        return first == null;
    }

    public int size()
    {
        int count=0;
        Node p = first;
        while(p!=null)
        {
            count++;
            p=p.next;
        }
        return count;
    }

    public void add(String e)
    {
        if(isEmpty())
        {
            first = new Node(e);
            last = first;
        }
        else
        {
            last.next = new Node(e);
            last = last.next;
        }
    }
    public void add(int index, String e)
    {
        if(index<0 || index>size())
        {
            String message = String.valueOf(index);
            throw new IndexOutOfBoundsException(message);
        }
        if(index==0)
        {
            first=new Node(e, first);
            if(last==null)
            {
                last=first;
                return;
            }
            Node pred = first;
            for(int k = 1; k<=index-1;k++)
            {
                pred=pred.next;
            }
            //splice in a node containging the new element
            pred.next = new Node(e, pred.next);
            //is theere a new last element?
            if(pred.next.next==null)
            {
                last = pred.next;
            }
        }
    }

    public String toString()
    {
        StringBuilder strBuilder = new StringBuilder();
        //use p to walk down linked list
        Node p = first;
        while(p!=null)
        {
            strBuilder.append(p.value+ "\n");
            p=p.next;
        }
        return strBuilder.toString();
    }

    public String remove(int index)
    {
        if(index<0||index>=size())
        {
            String message = String.valueOf(index);
            throw new IndexOutOfBoundsException(message);
        }
        String element;//element to return
        if(index==0)
        {
            //removal of the first element
            element = first.value;
            first = first.next;
            if(first==null)
                last=null;
        }
        else
        {
            //to remove an element other than the first, find the pred of the element to be removed
            Node pred = first;
            //move pred forward index-1 times
            for(int k = 1; k<=index-1;k++)
                pred=pred.next;
            //store the value to return
            element = pred.next.value;
            //Route link around the node to be removed
            pred.next = pred.next.next;
            //check if pred is now last
            if(pred.next==null)
                last=pred;
        }
        return element;
    }
    public boolean remove(String element)
    {
        if(isEmpty())
            return false;

        if(element.equals(first.value))
        {
            first = first.next;
            if(first==null)
                last=null;
            return true;
        }
        //find the pred of the element to remove
        Node pred = first;
        while(pred.next!= null && !pred.next.value.equals(element))
        {
            pred = pred.next;
        }

        //pred.next==null or pred.next.value is element
        if(pred.next==null)
            return false;
        //pred.next.value is element
        pred.next = pred.next.next;
        //check if pred is now last
        if(pred.next==null)
            last=pred;

        return true;
    }
    public static void main(String[] args)
    {
        LinkedList1 11 = new LinkedList1();
        11.add("Amy");
        11.add("Bob");
        11.add(0,"Al");
        11.add(2,"Beth");
        11.add(4,"Carol");
        System.out.println("The members of the list are: ");
        System.out.println(11);


    }
}

Answer 1

main 方法有一个不带字母的变量名。把 11 改成 tt 就可以了

Answer 2

改变 LinkedList1 11 = new LinkedList1(); 到 LinkedList 11 = new LinkedList();。