Java 替换字符串中除指定特殊子字符串外的所有字符的方法

实现的效果示例：

plusOut("12xy34", "xy") → "++xy++"
plusOut("12xy34", "1") → "1+++++"
plusOut("12xy34xyabcxy", "xy") → "++xy++xy+++xy"
plusOut("abXYabcXYZ", "ab") → "ab++ab++++"
plusOut("abXYabcXYZ", "abc") → "++++abc+++"
plusOut("abXYabcXYZ", "XY") → "++XY+++XY+"
plusOut("abXYxyzXYZ", "XYZ") → "+++++++XYZ"
plusOut("--++ab", "++") → "++++++"
plusOut("aaxxxxbb", "xx") → "++xxxx++"
plusOut("123123", "3") → "++3++3"

1、使用StringBuilder和for循环实现

public String plusOut(String str, String word) {
  StringBuilder out = new StringBuilder(str);
  for (int i = 0; i < out.length(); ) {
    if (!str.startsWith(word, i))
      out.setCharAt(i++, '+');
    else
      i += word.length();
  }
  return out.toString();
}

2、使用replaceAll和正则表达式实现

public String plusOut(String str, String word) {
    return str.replaceAll(java.util.regex.Pattern.quote(word), "@").replaceAll("[^@]", "+").replaceAll("@", word);
}

3、使用正则表达式\G实现

public String plusOut(String str, String word) {
  word = java.util.regex.Pattern.quote(word);
  return str.replaceAll("\\G((?:" + word + ")*+).", "$1+");
}

4、使用stream实现

public String plusOut(String str, String word) {
  return String.join(word, 
    Arrays.stream(str.split(java.util.regex.Pattern.quote(word), -1))
      .map((String s) -> s.replaceAll("(?s:.)", "+"))
      .collect(Collectors.toList()));
}