java.util.ConcurrentModificationException &迭代? [英] java.util.ConcurrentModificationException & iteration?

问题描述

我对 Arraylists & 非常陌生迭代器这是我第一次得到这个例外.我有一个 ArrayList u &我想做以下算法:

I'm so very new to Arraylists & iterators & this is the first time I got this exception. I have an ArrayList u & I'd like to do the following algorithm:

for (Character c:u){

    if(k==1){           //base case

        if(isAnswer(s+u.get(0)))

            System.out.println(s+u.get(0)+" is the correct sequence."+ '\n');
        return;
    }

    else{
        u.remove(c);
        puzzleSolve(k-1, s+c , u);
        u.add(c);
        removeLastChar(s);
    }

    } //end of for each

当我稍微搜索这个异常时，我发现我无法删除数组列表中的每个元素的 iterms &我需要使用迭代器但我很困惑在哪里&我必须如何准确地放置 while(iter.hasNext()) &这段代码的这些东西.如果你能帮助我，我将不胜感激

as I searched this exception a little bit i found out I can't remove iterms weth for each on a arraylist & I need to use iterator but i kinna got confused where & how exactly i must put the while(iter.hasNext()) & such stuff for this piece of code. i would be more than grateful if you could help me

附注.s 是字符串(最初为空)&k 是整数

PS. s is String ( initially empty) & k is int

推荐答案

我必须如何准确地放置 while(iter.hasNext())

您可以使用 iterator 如下:

Iterator<Character> iter = u.iterator();
while(iter.hasNext())
{
  Character c = iter.next();
  .....
}

用泛型初始化你的列表:Listu = new ArrayList();

Initialize your list with generics: List<Character> u = new ArrayList<Character>();

提示:在适用的地方使用 iter.remove()、iter.add() 而不是 u.remove() 和 u.add().

Hint: use iter.remove(), iter.add() wherever applicable instead of u.remove() and u.add().

您需要从这里开始:http://www.tutorialspoint.com/java/java_using_iterator.htm

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