我试图创建一个列表，因为它能够添加＆＃34;和元素相反，而不是检查大小，然后每次输入新元素时动态扩展数组。我无法编译。我已经搜集了堆栈和google，而我发现的任何东西都没有帮助我。有人提到创建一个数组并使用它添加到列表中，但在我看来，我应该能够做到这一点而没有这一切。
每次发生某个结果时，我都试图让系统在列表中添加一个字符串。
为了便于查找列表被调用＆＃34;不正确＆＃34;
import java.text.DecimalFormat;
import java.util.*;
public class User{
private String wrongQuestion; //quiz question
private String userName; //store user name
private String myOutput; //store output for toString and file write
private int score; //store user current score
private float average; //store user average score
private int diffLevel; //difficulty level
private int testType; //last test type
private int numTests; //store number of tests taken
private List <String> incorrect; //declare list for incorrect answers
private FileIO uFile; //declare FileIO object
public User(String inName) throws Exception
{
//local constants
final int VARIABLE_COUNT = 5; //loop sentinel
final int TOKEN_SKIP = 4; //loop sentinel
//local variables
int index; //loop index
int count; //loop counter
String token; //store tokens from line
StringTokenizer tokenLine; //store tokenized line
//instantiate file object
uFile = new FileIO (inName);
//if user exists
if (uFile.checkUser())
{
for (count = 0; count < VARIABLE_COUNT; count++)
{
//initialize tokenized line
tokenLine = new StringTokenizer(uFile.readLine());
//try to store the variables
try
{
//get and store user average
//for the first 2 tokens, skip
for (index = 0; index < TOKEN_SKIP; index++)
{
//move to next token
token = tokenLine.nextToken();//end for
switch (count)
{
case 1:
//store number of tests taken
numTests = Integer.parseInt(token);
//end case
break;
case 2:
//store difficulty of last test taken
diffLevel = Integer.parseInt(token);
//end case
break;
case 3:
//store score of last test taken
score = Integer.parseInt(token);
//end case
break;
case 4:
//store average of tests taken
average = Integer.parseInt(token);
//end case
break;
default:
break;
}//end switch
}//end for
//store next line
token = uFile.readLine();
//while there are more lines in the file
while (token != null)
{
//instantiate list for incorrect answers
incorrect = new ArrayList<String>();
//add line to end of list
incorrect.get(token);
//store next line
token = uFile.readLine();
}//end while
}//end try
//catch input mismatch exception
catch (InputMismatchException error)
{
//output error message
System.out.println ("This file is not formatted properly." +
" Either continue as a new user or log in again");
//initialize data to 0
average = 0;
testType = 0;
diffLevel = 0;
numTests = 0;
incorrect = new ArrayList <String>();
}//end catch
}//end for
}//end if
else
{
//initialize data to 0
average = 0;
testType = 0;
diffLevel = 0;
numTests = 0;
incorrect = new ArrayList<String>();
}//end else
//close input stream
uFile.closeFileReader();
}//end constructor
public float calcAverage(int newScore)
{
//local constants
//local variables
float avg; //store temp average
/**************Begin calcAverage*********/
//recalibrate avg for new calculation
avg = 0;
//calculate new average test score
avg = ((average * numTests) + newScore )/(numTests + 1);
//return average to be stored
return avg;
}
public void updateUser(int newTestType, int newDiffLevel, int newScore)
{
//local constants
//local variables
/***************Begin updateUser************/
//update new data after test is taken
score = newScore;
average = calcAverage(newScore);
diffLevel = newDiffLevel;
testType = newTestType;
numTests = numTests + 1;
}
public void writeFile() throws Exception
{
//local constants
//local variables
String line; //current line to write to file
int index; //loop index
/*************************Begin writeFile***************/
//open output stream
uFile.openOutput(userName);
//write user name
line = "User Name:\t" + userName +"\n";
uFile.writeLine(line);
//write number of tests taken
line = "Tests Taken:\t" + numTests + "\n";
//write number of tests taken
line = "Difficulty Level:\t" + diffLevel + "\n";
uFile.writeLine(line);
//write score of last test taken
line = "Last Test:\t" + score + "\n";
uFile.writeLine(line);
//write current user average
line = "User Average:\t" + average + "\n";
uFile.writeLine(line);
//for each element in the list
for (index = 0; index < incorrect.size(); index++)
{
//store then write the string
line = incorrect.get(index);
uFile.writeLine(line);
}//end for
//close file writer
uFile.closeFileWrite();
}//end writeFile
public void storeIncorrect(String inString)
{
//local constants
//local variables
/************Begin storeIncorrect*************/
//add formatted question to the list
incorrect.add(inString);
}
public String toString()
{
//local constants
//local variables
String buildUserName;
String buildAvg;
String buildNumTests;
String buildDiffLevel;
String buildScore;
DecimalFormat fmt; //declare decimal format object
/****************Begin toString***********/
//initialize decimal format
fmt = new DecimalFormat ("0.00");
//build output strings
buildUserName = Util.setLeft(20, "User Name:") + Util.setRight(25, userName);
buildNumTests = Util.setLeft(20, "Tests Taken:") + Util.setRight(18, numTests+"");
buildDiffLevel = Util.setLeft(20, "Last Difficulty:") + Util.setRight(24, diffLevel+"");
buildScore = Util.setLeft(20, "Last Score:") + Util.setRight(24, score+"");
buildAvg = Util.setLeft(20, "Test Average:") + Util.setRight(24, fmt.format(average)+"");
myOutput = buildUserName + "\n" + buildNumTests + "\n" + buildDiffLevel + "\n" + buildScore + "\n" + buildAvg;
return myOutput;
}//Display all users info
}
答案 0 :(得分：0)
很少有评论可能会有所帮助：
// add line to end of list
incorrect.get(token); // <- change this to incorrect.add(token)
通过列表使用迭代：
for (String item : incorrect) {
System.out.printlnt(item);
}
此外，您不需要多次重新初始化列表
incorrect = new ArrayList<String>();
如果您想清除它，可以使用incorrect.clear()
由于您对随机访问（即通过索引）不感兴趣，也许您可以使用LinkedList代替ArrayList