java - 检查字符串的结尾，无需使用 Java 中的endsWith() 等内置方法

Question

我想检查字符串中的每个单词是否都有不同长度的特定结尾。我不能使用数组和方法，例如endsWith()。我唯一允许使用的方法是 charAt() 和 length()。

public class TextAnalyse {
    public static void main(String[] args) {
        System.out.println(countEndings("This is a test", "t"));
        System.out.println(countEndings("Waren sollen rollen", "en"));
        System.out.println(countEndings("The ending is longer then every single word", "abcdefghijklmn"));
        System.out.println(countEndings("Today is a good day", "xyz"));
        System.out.println(countEndings("Thist is a test", "t"));
        System.out.println(countEndings("This is a test!", "t"));
        System.out.println(countEndings("Is this a test?", "t"));
    }

    public static int countEndings(String text, String ending) {
        int counter = 0;
        int counting;
        int lastStringChar;

        for (int i = 0; i < text.length(); i++) {
            lastStringChar = 0;
            if (!(text.charAt(i) >= 'A' && text.charAt(i) <= 'Z' || text.charAt(i) >= 'a' && text.charAt(i) <= 'z') || i == text.length() - 1) {
                if( i == text.length() - 1 ){
                    lastStringChar = 1;
                }
                counting = 0;
                for (int j = 0; j + lastStringChar < ending.length() && i > ending.length(); j++) {
                    if (text.charAt(i - ending.length() + j + lastStringChar) == ending.charAt(j)) {
                        counting = 1;
                    } else {
                        counting = 0;
                    }
                }
                counter += counting;
            }
        }

        return counter;
    }
}

实际结果是我少了一个，我猜是因为它没有正确检查最后一个字符。

Answer 1

我能想到的最简单的解决方案如下:

检查单词是否以给定后缀结尾:

public static boolean endsWith(String word, String suffix) {
  if(suffix.length() > word.length()) {
    return false;
  }
  int textIndex = (word.length() - 1);
  int suffixIndex = (suffix.length() - 1);
  while(suffixIndex >= 0) {
    char textChar = word.charAt(textIndex);
    char suffixChar = suffix.charAt(suffixIndex);
    if(textChar != suffixChar) {
      return false;
    }
    textIndex--;
    suffixIndex--;
  }
  return true;
}

将给定的单词拆分，并使用上述方法来计算以给定结尾结尾的每个单词:

public static int countEndings(String text, String ending) {
  {
    //maybe remove punctuation here...
    //(if yes, use String.replace for example)
  }
  String[] words = text.split(" ");
  int counter = 0;
  for(String word: words) {
    if(endsWith(word, ending)) {
      counter++;
    }
  }
  return counter;
}

还要考虑删除不需要的标点符号，例如“!”或者 '？' (...) - 上述实现不会识别 String 中以 t 结尾的任何单词的计数 test!!