Java内部类迭代器问题

Question

我使用内心有困难Iterator.

private List<List<? extends HasWord>> sentences = new ArrayList<List<? extends HasWord>>(); 
private Iterator<String> wordIterator = new Words();
private class Words implements Iterator<String> {

    int currSentence = 0;
    int currWord = 0;

    @Override
    public boolean hasNext() {
        return currSentence != sentences.size() - 1 && currWord != sentences.get(currSentence).size() - 1;
    }

    @Override
    public String next() {
        String nextWord = sentences.get(currSentence).get(currWord).word();
        currSentence++;
        currWord++;

        return nextWord;
    }

    @Override
    public void remove() {
        throw new UnsupportedOperationException();          
    }

}

然后,我尝试迭代它:

for (String s : wordIterator) { //Error: Can only iterate over an array or an instance of java.lang.Iterable
            words.add(s);

但它不起作用.(请参阅有问题的行上的注释编译器错误).我在这做错了什么？

在工程说明中,做是解决问题的正确方法吗？我有一堆这种形式的循环:

    for (List<? extends HasWord> sent : sentences) {
        for (HasWord token : sent) {
            //do stuff
        }
        }

所以我决定一个Iterator会更清洁.这有点矫枉过正,还是有另外一种方法可以做到这一点？

Answer 1

有两个嵌套for循环来做这件事并没有根本错误,但我认为这会更清晰:

public class Words implements Iterator<String> {
  private final Iterator<HasWord> sentences;
  private Iterator<String> currentSentence;

  public boolean hasNext() {
    return currentSentence.hasNext() || sentences.hasNext();
  }

  public String next() {
    if (currentSentence.hasNext()) {
      return currentSentence.next();
    }
    currentSentence = sentences.next();
    return next(); // will return the first word of the next sentence
  }
  //remove() omitted for brevity
}

每次需要多个句子的迭代器时,返回此类的新实例,并sentences使用初始化字段sentences.iterator();

(在仔细阅读您的问题后编辑)