Question

我的代码抛出了一个我以前从未见过的错误。嘿！嘿！我想我正在学习;）无论如何，我做了一些阅读，并且当迭代中的一个列表在迭代中被修改时，通常会抛出此错误。但是，我很确定我没有修改它。虽然在partition（）上抛出了错误，但如果我没有在updateCurrentList（）中为currentList分配新值（通过注释掉代码），则程序不再抛出错误。这两个函数在我的play（）方法中一个接一个地调用，但是列表迭代应该在更改时完成。我错过了什么？我必须以某种方式关闭迭代器吗？

package hangman;
import java.io.*;
import java.util.*;
import javax.swing.JOptionPane;

public class Hangman {
    private Map<String, List<String>> wordPartitions; // groups words according to positions of guessed letter
    private List<String> currentList; // remaining possible words that fit the information given so far
    Set<Character> wrongGuesses; // holds all the "wrong" guesses so far
    StringBuilder guessString; // current state of the word being guessed
    String justHyphens; // for checking whether a guess was "wrong"

    // initialize fields
    // currentList should contain all (and only) words of length wordLength

// justHyphens and guessString should consist of wordLength hyphens
public Hangman(int wordLength) throws FileNotFoundException {
    this.currentList = new ArrayList<String>();
    addWords(wordLength);
    wrongGuesses = new HashSet();

    for(int i = 0; i < wordLength; i++) {
        justHyphens += "-";
    }
    guessString = new StringBuilder();
    wordPartitions = new HashMap();
}

private void addWords(int wordLength) throws FileNotFoundException {
    Scanner words = new Scanner(new File("lexicon.txt"));
    String word = "";

    while(words.hasNext()) {
        word = words.next();
        if (word.length() == wordLength) {
            currentList.add(word);
        }
    }
}

// main loop
public void play() {
    char choice;

    do {
        choice = getUserChoice();
        partition(choice);
        updateCurrentList(choice);
    } while (!gameOver());
        endMessage();
}

// display the guessString and the missed guesses
// and get the next guess
private char getUserChoice() {
   //generate a string from the incorrect choices char list
    String wrong = "";
    char letter;

    if(!wrongGuesses.isEmpty()) {
        Iterator<Character> letters = wrongGuesses.iterator();
        letter = letters.next(); 

        while(letters.hasNext()) {
            letter = letters.next();
            wrong += ", " + letter;
        }
    }

    String letterStr = JOptionPane.showInputDialog("Incorrect choices: "+ wrong +"\n Tested letters: "+ guessString.toString() +"\nplease input a letter.");
    return letterStr.charAt(0);
}


// use wordPartitions to partition currentList using
// keys returned by getPartitionKey()
private void partition(char choice) {

    String word = "";
    String key = "";
    List<String> tempList = new ArrayList<String>();

    Iterator<String> words = currentList.iterator();
    //Generate a key for each word and add to appropriate arraylist within map.
    while(words.hasNext()) {
        word = words.next();
        key = getPartitionKey(word, choice);

        if(wordPartitions.containsKey(key)) {
            tempList = wordPartitions.get(key);
            tempList.add(word);
            wordPartitions.put(key, tempList);
        } else {
            tempList.clear();
            tempList.add(word);
            wordPartitions.put(key, new ArrayList<String>());                
        }            
    }
}

// update currentList to be a copy of the longest partition
// if choice was "wrong", add choice to wrongGuesses
// if choice was "right", update guessString
private void updateCurrentList(char choice) {        
    String key = findLongestList();

    currentList = wordPartitions.get(key);

    if(key.equals(justHyphens)) {
        wrongGuesses.add(choice);
    } else {
        addLetterToGuessString(guessString, choice, key);
    }
}

private String findLongestList() {
    Set<String> keySet = wordPartitions.keySet();
    Iterator<String> keys = keySet.iterator();
    String maxKey = "";
    int maxKeyLength = 0;
    List<String> tempList;
    String tempKey = "";

    while(keys.hasNext()) {
        tempKey = keys.next();
        tempList = wordPartitions.get(tempKey);

        if(tempList.size() > maxKeyLength) {
            maxKeyLength = tempList.size();
            maxKey = tempKey;
        }
    }

    return maxKey;
}

// checks for end of game
private boolean gameOver() {
    return false;
}

// display the guessString and the missed guesses
// and print "Congratulations!"
private void endMessage() {
    JOptionPane.showMessageDialog(null, "Congrats, yo!");
}

// returns string with '-' in place of each
// letter that is NOT the guessed letter
private String getPartitionKey(String s, char c) {
    String word = "";
    String letter = Character.toString(c);
    for(int i = 0; i < s.length(); i++) {
        if(s.charAt(i) == c) {
            word += letter;
        } else {
            word += "-";
        }
    }

    return word;
}
// update guessString with the guessed letter
private void addLetterToGuessString(StringBuilder guessString, char letter, String key) {
    for(int i = 0; i < key.length(); i++) {
        if(key.charAt(i) != '-') {
            guessString.setCharAt(i, key.charAt(i)); 
        } 
    }
}

}

Answer 1

问题是你在迭代它时正在修改一个集合。

该集合为currentList，您正在partition()中对其进行迭代。在此处向tempList添加单词时修改它：

key = getPartitionKey(word, choice);

if(wordPartitions.containsKey(key)) {
    tempList = wordPartitions.get(key);
    tempList.add(word);
    wordPartitions.put(key, tempList);
} else {

为什么？因为之前您从updateCurrentList()调用了play()：

do {
    choice = getUserChoice();
    partition(choice);
    updateCurrentList(choice);
} while (!gameOver());

您更新了currentList：

String key = findLongestList();

currentList = wordPartitions.get(key);

因此，如果key返回的getPartitionKey(word, choice)与先前findLongestList()返回的密钥相同，则currentList将与tempList相同，所以你将修改你正在迭代的集合。

解决方案？如果tempList与currentList相同，请不要向其添加单词（根据定义，它已经包含了单词）。所以，你可以像那样重写if-else（我删除了一些无用的代码）：

if(wordPartitions.containsKey(key)) {
    tempList = wordPartitions.get(key);
} else {
    wordPartitions.put(key, new ArrayList<String>());                
}

if (tempList!=currentList) {
    tempList.add(word);
}

无法弄清楚是什么触发了“java.util.ConcurrentModificationException”

1 个答案: