好吧，所以我讨厌就一个如此模糊的问题寻求帮助，但我现在正在处理一个项目，该项目似乎没有任何编译时错误，但不会做它所要求的。简单地总结一下，这个项目是一个链表（无序列表，具体来说），它充当文本编辑器。它将文件作为命令行参数，然后将文档的每一行单独存储为列表中的节点。我不知道它是否肯定这样做，但在那之后，程序会接收特定的命令（键盘输入）并根据要求编辑或列出文件的文本。
问题是，我什至无法判断文件是否存储在列表中，因为每次我给命令 L for list 时，程序都会"跳过"它并继续前进，就好像什么都没有要求一样。可能是由于某种原因未存储该文件，或者 unorderedList 类的 toString 方法可能存在问题。
我所有类的代码如下：
public class LinearNode<T> {
//Begin by declaring the basic node and its data
private LinearNode<T> next;
private T element;
public LinearNode() {
//The basic null constructor
next = null;
element = null;
}
public LinearNode(T elem) {
//The overloaded constructor to create a node
next = null;
element = elem;
}
public LinearNode<T> getNext() {
//Get the node reference
return next;
}
public void setNext(LinearNode<T> node) {
//Create or redirect a node reference
next = node;
}
public T getElement() {
//Get the actual data stored in the node
return element;
}
public void setElement(T elem) {
//Create or redirect the node's data
element = elem;
}
}
对于列表
public abstract class LinkedList<T> implements ListADT<T>, UnorderedListADT<T> {
protected int count;
protected LinearNode<T> head, tail;
protected int modCount;
public LinkedList () {
count = 0;
head = null;
tail = null;
head = tail;
head.setNext(tail);
modCount = 0;
}
public T remove(T targetElement) throws EmptyCollectionException, ElementNotFoundException {
if(isEmpty())
throw new EmptyCollectionException("LinkedList");
boolean found = false;
LinearNode<T> previous = null;
LinearNode<T> current = head;
while(current!=null&&!found) {
if(targetElement.equals(current.getElement())) {
found = true;
}
else {
previous = current;
current = current.getNext();
}
}
if(!found)
throw new ElementNotFoundException("Linked List");
if(size()==1) {
head = tail = null;
}
else if(current.equals(head))
head = current.getNext();
else if(current.equals(tail)) {
tail = previous;
tail.setNext(null);
}
else {
previous.setNext(current.getNext());
}
count--;
modCount++;
return current.getElement();
}
}
import java.util.Iterator;
public class UnorderedList<T> extends LinkedList<T>{
public UnorderedList() {
super();
}
public void addToFront(T element) {
if(head==null) {
head = new LinearNode<T>(element);
if(tail==null) {
tail = head;
}
count++;
modCount++;
}
else {
LinearNode<T> current = head;
head.setElement(element);
head.setNext(current);
count++;
modCount++;
}
}
public void addToRear(T element) {
if(tail.getElement()==null) {
tail.setElement(element);
count++;
modCount++;
}
else {
LinearNode<T> current = tail;
tail = new LinearNode<T>(element);
current.setNext(tail);
count++;
modCount++;
}
}
public void addAfter(T element, T target) {
LinearNode<T> current = head;
LinearNode<T> node = new LinearNode<T>(element);
LinearNode<T> temp = null;
while(!(current.getElement()==target)) {
current = current.getNext();
}
if(!(current.getNext()==null)) {
temp = current.getNext();
//temp.setElement(current.getElement());
}
current.setNext(node);
node.setNext(temp);
count++;
modCount++;
}
public T removeLast() {
T last = tail.getElement();
tail = null;
LinearNode<T> current = head;
while(!(current.getNext()==null)) {
current = current.getNext();
}
current = tail;
count--;
modCount++;
return last;
}
public int size() {
return count;
}
public Iterator<T> iterator() {
Iterator<T> itr = this.iterator();
return itr;
}
public boolean isEmpty() {
boolean result = false;
if(head==null&&tail==null) {
result = true;
}
else
result = false;
return result;
}
public T first() {
return head.getElement();
}
public T last() {
return tail.getElement();
}
public boolean contains(T elem) {
boolean result = false;
for(T element : this) {
if(element==elem) {
result = true;
break;
}
}
return result;
}
public T removeFirst() {
LinearNode<T> current = head;
head = current.getNext();
count--;
modCount++;
return current.getElement();
}
public String toString() {
LinearNode<T> current = head;
String s = "";
for(int countA=0;countA<count;count++) {
s += (countA+1)+"> "+current.getElement()+"n";
current = current.getNext();
}
return s;
}
}
对于主编
import java.util.Scanner;
import java.util.Iterator;
import java.io.*;
public class myEditor {
public static void saveToFile(String text, String filename) throws IOException{
PrintWriter out = new PrintWriter(new File(filename));
out.println(text);
out.close();
}
public static void main(String args[]) {
boolean quit = false;
try {
if(args.length!=1) {
throw new IllegalArgumentException();
}
String filename = args[0];
Scanner input = new Scanner(new File(filename));
//Add exception
UnorderedList<String> list = new UnorderedList<String>();
while(input.hasNextLine()) {
if(list.head==null) {
list.addToFront(input.nextLine());
}
list.addToRear(input.nextLine());
}
System.out.println(">");
do {
Scanner command = new Scanner(System.in);
String comm = command.next();
String[] comm1 = comm.split(" ");
if(comm1.length==1) {
if(comm1[0].equalsIgnoreCase("I")) {
System.out.println("Type a line of text >");
comm = command.next();
list.addToRear(comm);
}
else if(comm1[0].equalsIgnoreCase("L")) {
System.out.print(list.toString());
}
else if(comm1[0].equalsIgnoreCase("E")) {
saveToFile(list.toString(), filename);
quit = true;
break;
}
}
else {
if(comm1[0].equalsIgnoreCase("I")) {
int linNum = Integer.parseInt(comm1[1]);
Iterator<String> itr = list.iterator();
String current = "";
for(int count=0;count<linNum;count++) {
current = itr.next();
}
list.addAfter(comm, current);
}
else if(comm1[0].equalsIgnoreCase("D")) {
int linNum = Integer.parseInt(comm1[1]);
if(linNum<=list.count&&linNum>0) {
Iterator<String> itr = list.iterator();
String current = "";
for(int count=0;count<linNum;count++) {
current = itr.next();
}
list.remove(current);
}
}
}
}
while(!quit);
}
catch(IllegalArgumentException e) {
System.err.print(e.getMessage());
}
catch(FileNotFoundException e) {
System.err.print(e.getMessage());
}
catch(IOException e) {
System.err.print(e.getMessage());
}
}
}
还有一些其他类和一些接口，但对于我遇到的问题，我认为它们并不那么相关。
有没有人看到这里可能发生了什么，或者我可能写错了什么导致我的程序忽略该命令？
查看你的LinkedList构造函数
head = null;
tail = null;
head = tail;
head.setNext(tail);
head为 null 但您调用其 setNext 方法，它应该抛出一个 NPE。