String.split()分割字符串，转义字符

待我称王封你为后i 2022-05-23 00:11 434阅读 0赞

1、String.split()

String有个方法是分割字符串  .split()。但是有写字符串是需要转义才能分割，不然就会出错。

需要转义的字符串：.  $  |   (   )  \[   \{   ^  ?  \*  +  \\\\      共12个特殊字符，遇到以这些字符进行分割字符串的时候，需要在这些特殊字符前加双反斜杠 \\\\

例如：

str.split("\\\\.")

str.split("\\\\$")

str.split("\\\\|")

str.split("\\\\(")

str.split("\\\\)")

str.split("\\\\\[")

str.split("\\\\\{")

str.split("\\\\^")

str.split("\\\\?")

str.split("\\\\\*")

str.split("\\\\+")

str.split("\\\\\\\\")

2、源码：

public String[] split(String regex) {
            return split(regex, 0);
        }  
    public String[] split(String regex, int limit) {
            /* fastpath if the regex is a
             (1)one-char String and this character is not one of the
                RegEx's meta characters ".$|()[{^?*+\\", or
             (2)two-char String and the first char is the backslash and
                the second is not the ascii digit or ascii letter.
             */
            char ch = 0;
            if (((regex.value.length == 1 &&
                ".$|()[{^?*+\\".indexOf(ch = regex.charAt(0)) == -1) ||
                 (regex.length() == 2 &&
                  regex.charAt(0) == '\\' &&
                  (((ch = regex.charAt(1))-'0')|('9'-ch)) < 0 &&
                  ((ch-'a')|('z'-ch)) < 0 &&
                  ((ch-'A')|('Z'-ch)) < 0)) &&
                (ch < Character.MIN_HIGH_SURROGATE ||
                 ch > Character.MAX_LOW_SURROGATE))
            {
                int off = 0;
                int next = 0;
                boolean limited = limit > 0;
                ArrayList<String> list = new ArrayList<>();
                while ((next = indexOf(ch, off)) != -1) {
                    if (!limited || list.size() < limit - 1) {
                        list.add(substring(off, next));
                        off = next + 1;
                    } else {    // last one
                        //assert (list.size() == limit - 1);
                        list.add(substring(off, value.length));
                        off = value.length;
                        break;
                    }
                }
                // If no match was found, return this
                if (off == 0)
                    return new String[]{this};
    
                // Add remaining segment
                if (!limited || list.size() < limit)
                    list.add(substring(off, value.length));
    
                // Construct result
                int resultSize = list.size();
                if (limit == 0)
                    while (resultSize > 0 && list.get(resultSize - 1).length() == 0)
                        resultSize--;
                String[] result = new String[resultSize];
                return list.subList(0, resultSize).toArray(result);
            }
            return Pattern.compile(regex).split(this, limit);
        }