Dart -查找字符串中最常见的字符

String findMostCommonCharacter(String str) {
  Map<String, int> charCount = {};
  
  for (int i = 0; i < str.length; i++) {
    String char = str[i];
    if (charCount.containsKey(char)) {
      charCount[char]++;
    } else {
      charCount[char] = 1;
    }
  }
  
  String mostCommonChar;
  int maxCount = 0;
  
  charCount.forEach((char, count) {
    if (count > maxCount) {
      mostCommonChar = char;
      maxCount = count;
    }
  });
  
  return mostCommonChar;
}

void main() {
  String str = "Hello, World!";
  String mostCommonChar = findMostCommonCharacter(str);
  print("The most common character in the string is: $mostCommonChar");
}