Java 有没有办法将csv字符串拆分为40个字符，并用正则表达式删除最后一个逗号之后的任何内容？

在java项目中，存储逗号分隔值字符串的限制为40个字符。我们只需要显示尽可能多的值，因为对于一个报表来说，当值超过40个字符时，显示所有值并不重要。正则表达式是否可以在删除最后一个逗号中的字符时将字符串限制为40个字符

目前代码看起来像这样

String csv = "11111,22222,33333,44444,55555,66666,77777,88888,99999,00000";
String csvSub40 = csv.substring(0, 40);
String csvSub40LastComma = csvSub40.substring(0, csv.lastIndexOf(","));
//output is 11111,22222,33333,44444,55555,66666 as expected

我在正则表达式中尝试了一些方法，但不知道如何在不破坏字符串短于40个字符的情况下强制它查找最后一个逗号

5/13测试通过：

^(.{1,40})

9/13测试通过（反向）：

我这里有一个带有测试的regex101示例：

编辑：为了澄清那些没有查看regex101测试用例的人，这里是所有的测试用例

"11111" -> "11111"
"11111   " -> "11111"
"11111," -> "11111"
"11111,   " -> "11111"
"11111,22222,33333,44444,55555" -> "11111,22222,33333,44444,55555"
"11111,22222,33333,44444,55555   " -> "11111,22222,33333,44444,55555"
"11111,22222,33333,44444,55555," -> "11111,22222,33333,44444,55555"
"11111,22222,33333,44444,55555,   " -> "11111,22222,33333,44444,55555"
"11111,22222,33333,44444,55555,66666" -> "11111,22222,33333,44444,55555,66666"
"11111,22222,33333,44444,55555,66666   " -> "11111,22222,33333,44444,55555,66666"
"11111,22222,33333,44444,55555,66666," -> "11111,22222,33333,44444,55555,66666"
"11111,22222,33333,44444,55555,66666,   " -> "11111,22222,33333,44444,55555,66666"
"11111,22222,33333,44444,55555,66666,77777,88888,99999,00000" -> "11111,22222,33333,44444,55555,66666"
"11111,22222,33333,44444,55555,66666,77777,88888,99999,00000   " -> "11111,22222,33333,44444,55555,66666"
"11111,22222,33333,44444,55555,66666,77777,88888,99999,00000," -> "11111,22222,33333,44444,55555,66666"
"11111,22222,33333,44444,55555,66666,77777,88888,99999,00000,   " -> "11111,22222,33333,44444,55555,66666"

---

这应涵盖所有测试。正则表达式几乎不需要任何帮助（来自另一个正则表达式）来修剪行尾空格和悬空逗号

 String[] tests = {
                "11111", "11111",
                "11111   ", "11111",
                "11111,", "11111",
                "11111,   ", "11111",
                "11111,22222,33333,44444,55555", "11111,22222,33333,44444,55555",
                "11111,22222,33333,44444,55555   ", "11111,22222,33333,44444,55555",
                "11111,22222,33333,44444,55555,", "11111,22222,33333,44444,55555",
                "11111,22222,33333,44444,55555,   ", "11111,22222,33333,44444,55555",
                "11111,22222,33333,44444,55555,66666", "11111,22222,33333,44444,55555,66666",
                "11111,22222,33333,44444,55555,66666   ", "11111,22222,33333,44444,55555,66666",
                "11111,22222,33333,44444,55555,66666,", "11111,22222,33333,44444,55555,66666",
                "11111,22222,33333,44444,55555,66666,   ", "11111,22222,33333,44444,55555,66666",
                "11111,22222,33333,44444,55555,66666,77777,88888,99999,00000", "11111,22222,33333,44444,55555,66666",
                "11111,22222,33333,44444,55555,66666,77777,88888,99999,00000   ", "11111,22222,33333,44444,55555,66666",
                "11111,22222,33333,44444,55555,66666,77777,88888,99999,00000,", "11111,22222,33333,44444,55555,66666",
                "11111,22222,33333,44444,55555,66666,77777,88888,99999,00000,   ", "11111,22222,33333,44444,55555,66666"};

        Pattern p = Pattern.compile("((.{1,40})(,|$))");

        for (int i = 0; i < tests.length; i += 2) {
            String trimmed = tests[i].replaceAll(",?\\s*$", "");
            Matcher m = p.matcher(trimmed);

            if (m.find()) {    
                String g = m.group(2);

                if (!(tests[i + 1].equals(g))) {
                    System.out.println("Failed: \"" + g + "\"");         
                }
            } else {         
                System.out.println("Not Found: \"" + tests[i] + "\"");
            }
    }

String[]测试={
"11111", "11111",
"11111   ", "11111",
"11111,", "11111",
"11111,   ", "11111",
"11111,22222,33333,44444,55555", "11111,22222,33333,44444,55555",
"11111,22222,33333,44444,55555   ", "11111,22222,33333,44444,55555",
"11111,22222,33333,44444,55555,", "11111,22222,33333,44444,55555",
"11111,22222,33333,44444,55555,   ", "11111,22222,33333,44444,55555",
"11111,22222,33333,44444,55555,66666", "11111,22222,33333,44444,55555,66666",
"11111,22222,33333,44444,55555,66666   ", "11111,22222,33333,44444,55555,66666",
"11111,22222,33333,44444,55555,66666,", "11111,22222,33333,44444,55555,66666",
"11111,22222,33333,44444,55555,66666,   ", "11111,22222,33333,44444,55555,66666",
"11111,22222,33333,44444,55555,66666,77777,88888,99999,00000", "11111,22222,33333,44444,55555,66666",
"11111,22222,33333,44444,55555,66666,77777,88888,99999,00000   ", "11111,22222,33333,44444,55555,66666",
"11111,22222,33333,44444,55555,66666,77777,88888,99999,00000,", "11111,22222,33333,44444,55555,66666",
"11111,22222,33333,44444,55555,66666,77777,88888,99999,00000,   ", "11111,22222,33333,44444,55555,66666"};
Pattern p=Pattern.compile（（.{1,40}）（，|$）”；
对于（int i=0；i

这应该涵盖所有测试。正则表达式几乎不需要任何帮助（来自另一个正则表达式）来修剪行尾空格和悬空逗号

 String[] tests = {
                "11111", "11111",
                "11111   ", "11111",
                "11111,", "11111",
                "11111,   ", "11111",
                "11111,22222,33333,44444,55555", "11111,22222,33333,44444,55555",
                "11111,22222,33333,44444,55555   ", "11111,22222,33333,44444,55555",
                "11111,22222,33333,44444,55555,", "11111,22222,33333,44444,55555",
                "11111,22222,33333,44444,55555,   ", "11111,22222,33333,44444,55555",
                "11111,22222,33333,44444,55555,66666", "11111,22222,33333,44444,55555,66666",
                "11111,22222,33333,44444,55555,66666   ", "11111,22222,33333,44444,55555,66666",
                "11111,22222,33333,44444,55555,66666,", "11111,22222,33333,44444,55555,66666",
                "11111,22222,33333,44444,55555,66666,   ", "11111,22222,33333,44444,55555,66666",
                "11111,22222,33333,44444,55555,66666,77777,88888,99999,00000", "11111,22222,33333,44444,55555,66666",
                "11111,22222,33333,44444,55555,66666,77777,88888,99999,00000   ", "11111,22222,33333,44444,55555,66666",
                "11111,22222,33333,44444,55555,66666,77777,88888,99999,00000,", "11111,22222,33333,44444,55555,66666",
                "11111,22222,33333,44444,55555,66666,77777,88888,99999,00000,   ", "11111,22222,33333,44444,55555,66666"};

        Pattern p = Pattern.compile("((.{1,40})(,|$))");

        for (int i = 0; i < tests.length; i += 2) {
            String trimmed = tests[i].replaceAll(",?\\s*$", "");
            Matcher m = p.matcher(trimmed);

            if (m.find()) {    
                String g = m.group(2);

                if (!(tests[i + 1].equals(g))) {
                    System.out.println("Failed: \"" + g + "\"");         
                }
            } else {         
                System.out.println("Not Found: \"" + tests[i] + "\"");
            }
    }

String[]测试={
"11111", "11111",
"11111   ", "11111",
"11111,", "11111",
"11111,   ", "11111",
"11111,22222,33333,44444,55555", "11111,22222,33333,44444,55555",
"11111,22222,33333,44444,55555   ", "11111,22222,33333,44444,55555",
"11111,22222,33333,44444,55555,", "11111,22222,33333,44444,55555",
"11111,22222,33333,44444,55555,   ", "11111,22222,33333,44444,55555",
"11111,22222,33333,44444,55555,66666", "11111,22222,33333,44444,55555,66666",
"11111,22222,33333,44444,55555,66666   ", "11111,22222,33333,44444,55555,66666",
"11111,22222,33333,44444,55555,66666,", "11111,22222,33333,44444,55555,66666",
"11111,22222,33333,44444,55555,66666,   ", "11111,22222,33333,44444,55555,66666",
"11111,22222,33333,44444,55555,66666,77777,88888,99999,00000", "11111,22222,33333,44444,55555,66666",
"11111,22222,33333,44444,55555,66666,77777,88888,99999,00000   ", "11111,22222,33333,44444,55555,66666",
"11111,22222,33333,44444,55555,66666,77777,88888,99999,00000,", "11111,22222,33333,44444,55555,66666",
"11111,22222,33333,44444,55555,66666,77777,88888,99999,00000,   ", "11111,22222,33333,44444,55555,66666"};
Pattern p=Pattern.compile（（.{1,40}）（，|$）”；
对于（int i=0；i

看起来这就是你要找的：

Pattern=Pattern.compile（“^（\\S{0,39}[^\\S，]）（？=（，| \\S+|$））”；
Matcher Matcher=pattern.Matcher（csv）；
字符串csvsub40lastcoma=matcher.find（）？匹配器组（1）：“”；

除了匹配正则表达式外，无需执行任何操作

---

你可以玩这个正则表达式。

看起来这就是你要找的：

Pattern=Pattern.compile（“^（\\S{0,39}[^\\S，]）（？=（，| \\S+|$））”；
Matcher Matcher=pattern.Matcher（csv）；
字符串csvsub40lastcoma=matcher.find（）？匹配器组（1）：“”；

除了匹配正则表达式外，无需执行任何操作

---

您可以使用这个正则表达式。

我建议您使用

String#substring

。只需在逗号上拆分字符串，并根据指定的长度迭代生成的数组（例如。

import java.util.Arrays;

public class Main {
    public static void main(String[] args) {
        String[] csvArr = { "11111,22222,33333,44444,55555,66666,77777,88888,99999,00000", "11111", "11111   ",
                "11111,", "11111,   ", "11111,22222,33333,44444,55555", "11111,22222,33333,44444,55555   ",
                "11111,22222,33333,44444,55555,", "11111,22222,33333,44444,55555,   ",
                "11111,22222,33333,44444,55555,66666", "11111,22222,33333,44444,55555,66666   ",
                "11111,22222,33333,44444,55555,66666,", "11111,22222,33333,44444,55555,66666,   ",
                "11111,22222,33333,44444,55555,66666,77777,88888,99999,00000",
                "11111,22222,33333,44444,55555,66666,77777,88888,99999,00000   ",
                "11111,22222,33333,44444,55555,66666,77777,88888,99999,00000,",
                "11111,22222,33333,44444,55555,66666,77777,88888,99999,00000,   " };

        for (String csv : csvArr) {
            String[] values = csv.split(",");
            int i = 0, sum = 0;
            for (i = 0; i < values.length && sum + values[i].length() <= 40; i++, sum++) {
                sum += values[i].length();
            }
            String result = String.join(",", Arrays.copyOf(values, i)).trim();

            // Drop the last character if it's a comma
            int len = result.length();
            result = result.lastIndexOf(",") == len - 1 ? result.substring(0, len - 1) : result;

            System.out.println(result);
        }
    }
}

11111,22222,33333,44444,55555,66666
11111
11111
11111
11111
11111,22222,33333,44444,55555
11111,22222,33333,44444,55555
11111,22222,33333,44444,55555
11111,22222,33333,44444,55555
11111,22222,33333,44444,55555,66666
11111,22222,33333,44444,55555,66666
11111,22222,33333,44444,55555,66666
11111,22222,33333,44444,55555,66666
11111,22222,33333,44444,55555,66666
11111,22222,33333,44444,55555,66666
11111,22222,33333,44444,55555,66666
11111,22222,33333,44444,55555,66666