我的程序和测试类提供了这个非常奇怪的问题。目标是以提供的确切格式返回一个字符串。但是，当我运行测试类时，它告诉我我的字符串是错误的，即使它与测试类中的字符串完全相同。即使字符串是正确的，我也不确定它为什么会出现错误的字符串。谢谢！ 这是班级：
public class RecursionLinkedList
{
private Node firstNode;
private int numberOfEntries;
public RecursionLinkedList()
{
firstNode = null;
numberOfEntries = 0;
}
public void add(int aData)
{
if(numberOfEntries == 0)
{
firstNode = new Node(aData);
}
else
{
firstNode = new Node(aData, firstNode);
}
numberOfEntries++;
}
/**
* boolean contains(int aData)
*
* See whether this RecursionLinkedList contains aData
* @param aData a data to be located
* @return true if this RecursionLinkedList contains aData,
* or false otherwise.
*/
public boolean contains(int aData)
{
Node currentNode = firstNode;
if(currentNode == null) {
return false;
}
if(currentNode.data == aData) {
return true;
}
else {
return contains1(aData, currentNode);
}
}
/**
* int getFrequencyOf(int aData)
*
* Counts the number of times a given data appears in this
* RecursionLinkedList.
*
* @param aData the data to be counted
* @return the number of times aData appears in this RecursionLinkedList
*/
public int getFrequencyOf(int aData)
{
Node currentNode = firstNode;
int frequency = 0;
if(currentNode == null) {
return frequency;
}
else {
frequency = getFrequencyOf1(aData, currentNode);
return frequency;
}
}
/**
* String toString()
*
* Return a string representation of this RecursionLinkedList. For example,
* if this RecursionLinkedList contains 1, 2, 3, 5, 2 and 3 from the first
* index to the last index, the returned string should be
* "[1,2,3,5,2,3]"
* @return the string representation of this RecursionLinkedList.
*/
public String toString()
{
Node currentNode = firstNode;
String str1 = "[";
String str = toString1(currentNode);
String str2 = "]";
return str1 + str + str2;
}
/**
* int getIndexOf(int aData)
*
* Return the index of the first aData where the first index of
* the first item in this RecursionLinkedList is 0.
*
* @param aData the data to be located
* @return the index of the first aData.
*/
public int getIndexOf(int aData)
{
Node currentNode = firstNode;
int index = 0;
if(currentNode == null) {
return 0;
}
else {
index = getIndexOf1(aData, currentNode);
return index;
}
}
public boolean contains1(int aData, Node node)
{
Node currentNode = node;
if(currentNode == null) {
return false;
}
if(currentNode.data == aData) {
return true;
}
else {
return contains1(aData, currentNode.next);
}
}
public int getFrequencyOf1(int aData, Node node)
{
Node currentNode = node;
int frequency = 0;
if(currentNode == null) {
return frequency;
}
if(currentNode.data == aData) {
frequency = 1 + getFrequencyOf1(aData, currentNode.next);
}
else {
frequency = getFrequencyOf1(aData, currentNode.next);
}
return frequency;
}
public String toString1(Node node)
{
Node currentNode = node;
if(currentNode == null) {
return "\b";
}
else {
int i = currentNode.data;
String str = Integer.toString(i);
String str1 = str + ","+toString1(currentNode.next);
return str1;
}
}
public int getIndexOf1(int aData, Node node)
{
Node currentNode = node;
int index = 0;
if(currentNode == null) {
return 0;
}
if(currentNode.data == aData) {
return index;
}
else {
index = 1 + getIndexOf1(aData, currentNode.next);
return index;
}
}
private class Node
{
private int data;
private Node next;
private Node(int aData, Node nextNode)
{
data = aData;
next = nextNode;
}
private Node(int aData)
{
this(aData, null);
}
}
}
这是测试类：
import java.util.Random;
public class RecursionLLTester
{
public static void main(String[] args)
{
RecursionLinkedList rll = new RecursionLinkedList();
int point = 0;
boolean isError = false;
System.out.println("Create an empty RecursionLinkedList named rll.");
System.out.print("Test the method contains() on an empty RecursionLinkedList: ");
if(rll.contains(5) != false)
{
System.out.println("FAIL");
System.out.println("Nothing is added into RecursionLinkedList rll.");
System.out.println("rll.contains(5) should return 0.");
System.out.println("But your rll.contains(5) returns " + rll.contains(5) + ".");
}
else
{
System.out.println("PASS");
point++;
}
System.out.print("Test the method getFrequencyOf() on an empty RecursionLinkedList: ");
if(rll.getFrequencyOf(5) != 0)
{
System.out.println("FAIL");
System.out.println("Nothing is added into RecursionLinkedList rll.");
System.out.println("rll.getFrequencyOf(5) should return 0.");
System.out.println("But your rll.getFrequencyOf(5) returns " + rll.getFrequencyOf(5) + ".");
}
else
{
System.out.println("PASS");
point++;
}
Random rand = new Random();
int num = 20;
int[] array = new int[5];
for(int i = 0; i < 5; i++)
{
array[i] = 0;
}
System.out.println("Add the following integer into rll:");
String s = "]";
for(int i = 0; i < num - 1; i++)
{
int temp = rand.nextInt(5);
System.out.print(temp + " ");
s = "," + temp + s;
array[temp]++;
rll.add(temp);
}
int temp = rand.nextInt(5);
System.out.println(temp);
s = "[" + temp + s;
array[temp]++;
rll.add(temp);
System.out.println("\nTest the method contains() on a non-empty RecursionLinkedList");
System.out.print(" - Test rll.contains(-1): ");
if(rll.contains(-1) != false)
{
System.out.println("FAIL");
System.out.println("No -1 has been added into the RecursionLinkedList rll.");
System.out.println("rll.contains(-1) should return 0.");
System.out.println("But your rll.contains(-1) returns " + rll.contains(-1));
}
else
{
System.out.println("PASS");
point++;
}
for(int i = 0; i < 5; i++)
{
System.out.print(" - Test rll.contains(" + i + "): ");
if(rll.contains(i) != (array[i] != 0))
{
System.out.println("FAIL");
System.out.println("There are " + array[i] + " in RecursiveLinkedList rll.");
System.out.println("rll.contains(" + i + ") should return " + (array[i] != 0));
System.out.println("But your rll.contains(" + i + ") returns " + rll.contains(i));
isError = true;
}
else
{
System.out.println("PASS");
}
}
if(!isError)
{
point++;
isError = false;
}
System.out.print(" - Test rll.contains(5): ");
if(rll.contains(5) != false)
{
System.out.println("FAIL");
System.out.println("No 5 has been added into the RecursionLinkedList rll.");
System.out.println("rll.contains(5) should return 0.");
System.out.println("But your rll.contains(5) returns " + rll.contains(5));
}
else
{
System.out.println("PASS");
point++;
}
System.out.println("Test the method getFrequencyOf() on a non-empty RecursionLinkedList");
System.out.print(" - Test rll.getFrequencyOf(-1): ");
if(rll.getFrequencyOf(-1) != 0)
{
System.out.println("FAIL");
System.out.println("No -1 has been added into the RecursionLinkedList rll.");
System.out.println("rll.getFrequencyOf(-1) should return 0.");
System.out.println("But your rll.getFrequencyOf(-1) returns " + rll.getFrequencyOf(-1));
}
else
{
System.out.println("PASS");
point++;
}
for(int i = 0; i < 5; i++)
{
System.out.print(" - Test rll.getFrequencyOf(" + i + "): ");
if(rll.getFrequencyOf(i) != array[i])
{
System.out.println("FAIL");
System.out.println(i + " has been added to the RecursionLinkedList " + array[i] + " times.");
System.out.println("rll.getFrequencyOf(" + i + ") should return " + array[i] + ".");
System.out.println("But your rll.getFrequencyOf(" + i + ") returns " + rll.getFrequencyOf(i));
isError = true;
}
else
{
System.out.println("PASS");
}
}
if(!isError)
{
point++;
isError = false;
}
System.out.print(" - Test rll.getFrequencyOf(5): ");
if(rll.getFrequencyOf(5) != 0)
{
System.out.println("FAIL");
System.out.println("No 5 has been added into the RecursionLinkedList rll.");
System.out.println("rll.getFrequencyOf(5) should return 0.");
System.out.println("But your rll.getFrequencyOf(5) returns " + rll.getFrequencyOf(5));
}
else
{
System.out.println("PASS");
point++;
}
System.out.print("Test the method toString(): ");
if(!s.equals(rll.toString()))
{
System.out.println("FAIL");
System.out.println("rll.toString() should return the string \"" + s + "\".");
System.out.println("But your rll.toString() returns the string \"" + rll.toString() + "\".");
}
else
{
System.out.println("PASS");
point++;
}
System.out.println("Test the method getIndexOf()");
System.out.println("Currently the rll is " + rll + ".");
String[] str = rll.toString().split(",");
str[0] = str[0].substring(1);
str[str.length - 1] = str[str.length - 1].substring(0, 1);
for(int i = -1; i <= 5; i++)
{
System.out.print("Test the method getIndexOf(" + i + "): ");
if(getIndex(str,i) != rll.getIndexOf(i))
{
System.out.println("FAIL");
System.out.println("The index of " + i + " should be " + getIndex(str,i) + ".");
System.out.println("But your rll.getIndexOf(" + i + ") returns " + rll.getIndexOf(i) + ".");
isError = true;
}
else
{
System.out.println("PASS");
}
}
if(!isError)
{
point++;
isError = false;
}
System.out.println("Your current point is " + point + ".");
}
public static int getIndex(String[] str, int s)
{
int result = -1;
for(int i = 0; i < str.length; i++)
{
if(s == Integer.parseInt(str[i]))
{
return i;
}
}
return result;
}
}
答案 0 :(得分：0)
问题在于您的toString1(Node)方法。
if (currentNode == null) {
return "\b";
}
\b字符是您在测试输出结束时看到的字符。
rll.toString（）应返回字符串＆＃34; [1,1,1,3,4,2,2,1,0,1,2,1,0,4,4,4,2 ，1,1,2-]＆＃34;
但你的rll.toString（）返回字符串＆＃34; [1,1,1,3,4,2,2,1,0,1,2,1,0,4,4,4， ？2,1,1,2，]＆＃34;
稍微调整方法如下，有问题的测试通过。
public String toString1(Node node)
{
Node currentNode = node;
if (currentNode == null) {
return "\b";
}
int i = currentNode.data;
String str = Integer.toString(i);
if (currentNode.next != null) {
str = str
+ "," + toString1(currentNode.next);
}
return str;
}
虽然我建议你在这里改变一些事情：
StringBuilder而不是所有对字符串连接进行颠簸。\b字符，因为它不代表整数，而您的indexOf()方法似乎也在扼杀这个概念