split切割字符串注意事项

- 日理万妓 2022-06-08 02:05 438阅读 0赞

split()方法的源码：

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);
        }

**从源码中可以看出，split()方法是正则表达式，所以如果要使用到以下字符“.$|()\[\{^?\*+\\\\”作为切割符的话，需要进行转义，因为这些字符在正则表达式中属于一种有特殊含义的字符。**

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【1】单个符号作为分隔符

String address="上海|上海市|闵行区|吴中路";

String\[\] splitAddress=address.split("\\\\|"); //如果以竖线为分隔符，则split的时候需要加上两个斜杠【\\\\】进行转义

System.out.println(splitAddress\[0\]+splitAddress\[1\]+splitAddress\[2\]+splitAddress\[3\]);

String address="上海\*上海市\*闵行区\*吴中路";

String\[\] splitAddress=address.split("\\\\\*");

System.out.println(splitAddress\[0\]+splitAddress\[1\]+splitAddress\[2\]+splitAddress\[3\]);

String address="上海:上海市:闵行区:吴中路";

String\[\] splitAddress=address.split("\\\\:");

System.out.println(splitAddress\[0\]+splitAddress\[1\]+splitAddress\[2\]+splitAddress\[3\]);

String address="上海.上海市.闵行区.吴中路";

String\[\] splitAddress=address.split("\\\\.");

System.out.println(splitAddress\[0\]+splitAddress\[1\]+splitAddress\[2\]+splitAddress\[3\]);

String address="上海^上海市^闵行区^吴中路";

String\[\] splitAddress=address.split("\\\\^");

System.out.println(splitAddress\[0\]+splitAddress\[1\]+splitAddress\[2\]+splitAddress\[3\]);

String address="上海@上海市@闵行区@吴中路";

String\[\] splitAddress=address.split("@");

System.out.println(splitAddress\[0\]+splitAddress\[1\]+splitAddress\[2\]+splitAddress\[3\]);

String address="上海,上海市,闵行区,吴中路";

String\[\] splitAddress=address.split(",");

System.out.println(splitAddress\[0\]+splitAddress\[1\]+splitAddress\[2\]+splitAddress\[3\]);

【2】多个符号作为分隔符

String address="上海^上海市@闵行区\#吴中路";

String\[\] splitAddress=address.split("\\\\^|@|\#");

System.out.println(splitAddress\[0\]+splitAddress\[1\]+splitAddress\[2\]+splitAddress\[3\]);

\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\* 格式 小提示\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*

String address = new String("192.168.13.240");

String\[\] str = address.split("\\\\.");

for(String s : str)\{

System.out.println(s);

输出格式：

192

168

240

System.out.println(splitAddress\[0\]+splitAddress\[1\]+splitAddress\[2\]+splitAddress\[3\]);

输出格式：上海上海市闵行区吴中路

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总结：（1）split表达式，其实就是一个正则表达式。\*   ^ | 等符号在正则表达式中属于一种有特殊含义的字符，如果使用此种字符作为分隔符，必须使用转义符即\\\\加以转义。