問(wèn)題描述

我需要一個(gè)來(lái)自 String 對(duì)象的 Iterator<Character>.Java 中是否有任何可用函數(shù)可以為我提供此功能，還是我必須自己編寫(xiě)代碼?

I need a Iterator<Character> from a String object. Is there any available function in Java that provides me this or do I have to code my own?

推薦答案

一種選擇是使用 番石榴:

ImmutableList<Character> chars = Lists.charactersOf(someString);
UnmodifiableListIterator<Character> iter = chars.listIterator();

這會(huì)生成一個(gè)由給定字符串支持的不可變字符列表(不涉及復(fù)制).

This produces an immutable list of characters that is backed by the given string (no copying involved).

如果您最終自己這樣做，我建議不要像許多其他示例那樣公開(kāi) Iterator 的實(shí)現(xiàn)類(lèi).我建議改為創(chuàng)建自己的實(shí)用程序類(lèi)并公開(kāi)靜態(tài)工廠方法:

If you end up doing this yourself, though, I would recommend not exposing the implementation class for the Iterator as a number of other examples do. I'd recommend instead making your own utility class and exposing a static factory method:

public static Iterator<Character> stringIterator(final String string) {
  // Ensure the error is found as soon as possible.
  if (string == null)
    throw new NullPointerException();

  return new Iterator<Character>() {
    private int index = 0;

    public boolean hasNext() {
      return index < string.length();
    }

    public Character next() {
      /*
       * Throw NoSuchElementException as defined by the Iterator contract,
       * not IndexOutOfBoundsException.
       */
      if (!hasNext())
        throw new NoSuchElementException();
      return string.charAt(index++);
    }

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

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