Java中每第三个逗号分割一个字符串 [英] Split a String at every 3rd comma in Java

问题描述

我有一个看起来像这样的字符串:

I have a string that looks like this:

0,0,1,2,4,5,3,4,6

我想要返回的是一个 String[] 在每第三个逗号之后分割，所以结果看起来像这样:

What I want returned is a String[] that was split after every 3rd comma, so the result would look like this:

[ "0,0,1", "2,4,5", "3,4,6" ]

我发现了类似的函数，但它们不会在第 n 个逗号处拆分.

I have found similar functions but they don't split at n-th amount of commas.

推荐答案

您可以尝试将 split 方法与 (?<=\\G\\d+,\\d+,\\d+), 正则表达式

You can try to use split method with (?<=\\G\\d+,\\d+,\\d+), regex

演示

String data = "0,0,1,2,4,5,3,4,6";
String[] array = data.split("(?<=\\G\\d+,\\d+,\\d+),"); //Magic :) 
// to reveal magic see explanation below answer
for(String s : array){
    System.out.println(s);
}

输出:

0,0,1
2,4,5
3,4,6

说明

• \\d 表示一位，同[0-9]，如0或3
• \\d+ 表示一个或多个数字，如 1 或 23
• \\d+, 表示后面有逗号的一位或多位数字，如 1, 或 234,
• \\d+,\\d+,\\d+ 将接受三个数字，它们之间有逗号，如 12,3,456
• \\G 表示最后一次匹配，或者如果没有(在第一次使用的情况下)字符串开头
• (?<=...), 是 positive look-behind 将匹配逗号 , 也有一些在它之前的 (?<=...) 中描述的字符串
• (?<=\\G\\d+,\\d+,\\d+), 所以会尝试找到前面有三个数字的逗号，并且这些数字以以太开头之前的字符串(如您的示例中的 ^0,0,1)或之前匹配的逗号，如 2,4,5 和 3,4，6.

• \\d means one digit, same as [0-9], like 0 or 3
• \\d+ means one or more digits like 1 or 23
• \\d+, means one or more digits with comma after it, like 1, or 234,
• \\d+,\\d+,\\d+ will accept three numbers with commas between them like 12,3,456
• \\G means last match, or if there is none (in case of first usage) start of the string
• (?<=...), is positive look-behind which will match comma , that has also some string described in (?<=...) before it
• (?<=\\G\\d+,\\d+,\\d+), so will try to find comma that has three numbers before it, and these numbers have aether start of the string before it (like ^0,0,1 in your example) or previously matched comma, like 2,4,5 and 3,4,6.

另外，如果您想使用其他字符然后数字，您也可以使用其他字符集，例如

Also in case you want to use other characters then digits you can also use other set of characters like

• \\w 将匹配字母字符、数字和 _
• \\S 不是空白的所有内容
• [^,] 不是逗号的所有内容
• ...等等.模式文档

• \\w which will match alphabetic characters, digits and _
• \\S everything that is not white space
• [^,] everything that is not comma
• ... and so on. More info in Pattern documentation

顺便说一句，这种形式将在每第 3、5、7、(和其他奇数)逗号上进行拆分，例如 split("(?<=\\G\\w+,\\w+,\\w+,\\w+,\\w+),") 将在每 5 个逗号处拆分.

By the way, this form will work with split on every 3rd, 5th, 7th, (and other odd numbers) comma, like split("(?<=\\G\\w+,\\w+,\\w+,\\w+,\\w+),") will split on every 5th comma.

要在每 2、4、6、8(以及其余偶数)逗号上拆分，您需要将 + 替换为 {1,maxLengthOfNumber}，例如 <代码>split("(?<=\\G\\w{1,3},\\w{1,3},\\w{1,3},\\w{1,3}),") 当数字最多可以有 3 位数字(0、00、12、000、123、412、999)时，每 4 个逗号分割一次.

To split on every 2nd, 4th, 6th, 8th (and rest of even numbers) comma you will need to replace + with {1,maxLengthOfNumber} like split("(?<=\\G\\w{1,3},\\w{1,3},\\w{1,3},\\w{1,3}),") to split on every 4th comma when numbers can have max 3 digits (0, 00, 12, 000, 123, 412, 999).

要拆分每 2 个逗号，您还可以根据我的 以前的答案

To split on every 2nd comma you can also use this regex split("(?<!\\G\\d+),") based on my previous answer

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