Java String 的 split 方法忽略空子串 [英] Java String's split method ignores empty substrings

问题描述

今天我发现java String.split() 的行为很奇怪.

It occured to me today the behavior of java String.split() is very strange.

实际上我想通过 .split(",") 将字符串 "aa,bb,cc,dd,,,ee" 拆分为数组，这给了我一个字符串数组 ["aa","bb","cc","dd","","","ee"] 长度为 7.

Actually I want to split a string "aa,bb,cc,dd,,,ee" to array by .split(",") that gives me a String array ["aa","bb","cc","dd","","","ee"] of length 7.

但是当我尝试将字符串 "aa,bb,cc,dd,,,," 拆分为数组时，这给了我一个长度为 4 的数组，这意味着只有 ["aa","bb","cc","dd"] 拒绝所有接下来的空白字符串.

But when I try to split a String "aa,bb,cc,dd,,,," to array this gives me a array of length 4 means only ["aa","bb","cc","dd"] rejecting all next blank Strings.

我想要一个将像 "aa,bb,cc,dd,,,," 这样的字符串拆分为数组 ["aa","bb","cc","dd","","",""].

I want a procedure that splits a String like "aa,bb,cc,dd,,,," to array ["aa","bb","cc","dd","","",""].

这可以用 java.lang.String api 实现吗?提前致谢.

Is this possible with java.lang.String api? Thanks in advance.

推荐答案

使用 String.split(String regex, int limit) 带有负限制(例如 -1).>

"aa,bb,cc,dd,,,,".split(",", -1)

当 String.split(String regex) 被调用，它被调用时limit = 0，这将删除数组中所有尾随的空字符串(在大多数情况下)案例，见下文).

When String.split(String regex) is called, it is called with limit = 0, which will remove all trailing empty strings in the array (in most cases, see below).

String.split(String regex) 的实际行为相当混乱:

The actual behavior of String.split(String regex) is quite confusing:

• 拆分空字符串将生成长度为 1 的数组.拆分空字符串将始终生成包含空字符串的长度为 1 的数组.
• 将 ";" 或 ";;;" 与 regex 拆分为 ";" 将导致一个空数组.非空字符串拆分将导致删除数组中的所有尾随空字符串.

• Splitting an empty string will result in an array of length 1. Empty string split will always result in length 1 array containing the empty string.
• Splitting ";" or ";;;" with regex being ";" will result in an empty array. Non-empty string split will result in all trailing empty strings in the array removed.

至少从 Java 5 到 Java 8 都可以观察到上述行为.

The behavior above can be observed from at least Java 5 to Java 8.

尝试更改在 JDK-6559590.然而，它很快在 JDK-8028321 中被恢复，因为它在各个地方导致回归.该更改从未包含在最初的 Java 8 版本中.

There was an attempt to change the behavior to return an empty array when splitting an empty string in JDK-6559590. However, it was soon reverted in JDK-8028321 when it causes regression in various places. The change never makes it into the initial Java 8 release.

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