java - 从哈希集中删除项目

Question

我正在创建一个问答游戏。有些答案有替代答案，例如:

俄罗斯总统是谁？

• Vladimir Poetin
• Poetin

这是代码:

for (HashSet<String> answer : answers) {
    for (String alternative : answer) {
        // Apply levensthein
        int distance = levensthein(givenAnswer, alternative);
        double ratio = ((double) distance) / (Math.max(alternative.length(), givenAnswer.length()));
        // 20 % error margin
        if (ratio <= 0.2) {
            // remove this set of answers, so you can't try in the same answer again
            answers.remove(answer);
            return true;
        }
    }
}

在 levensthein 检查之后，必须将答案从 Hashset 中删除。它适用于问题没有替代答案的情况。

我怎样才能让它工作？有什么想法我做错了吗？

谢谢!

Answer 1

增强的 for 循环不适合从正在迭代的集合中删除元素。请改用显式迭代器。

Iterator<HashSet<String>> aIter = answers.iterator();
while (aIter.hasNext()) {
    HashSet<String> answer = aIter.next();
    Iterator<String> iter = answer.iterator();
    while (iter.hasNext()) {
        String alternative = iter.next();
        // Apply levensthein
        int distance = levensthein(givenAnswer, alternative);
        double ratio = ((double) distance) / (Math.max(alternative.length(), givenAnswer.length()));
        // 20 % error margin
        if (ratio <= 0.2) {
            // remove this set of answers, so you can't try in the same answer again
            aIter.remove();
            return true;
        }
    }
}