java 如何在匹配器组而不是整个模式上追加替换？
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How to appendReplacement on a Matcher group instead of the whole pattern?
提问by cottonBallPaws
I am using a while(matcher.find())to loop through all of the matches of a Pattern. For each instance or match of that pattern it finds, I want to replace matcher.group(3)with some new text. This text will be different for each one so I am using matcher.appendReplacement()to rebuild the original string with the new changes as it goes through. However, appendReplacement()replaces the entire Pattern instead of just the group.
我正在使用 awhile(matcher.find())来遍历模式的所有匹配项。对于它找到的该模式的每个实例或匹配项，我想matcher.group(3)用一些新文本替换。每个文本都会有所不同，因此我将使用matcher.appendReplacement()新的更改来重建原始字符串。但是，appendReplacement()替换整个 Pattern 而不仅仅是组。
How can I do this but only modify the third group of the match rather than the entire Pattern?
我怎样才能做到这一点，但只修改匹配的第三组而不是整个模式？
Here is some example code:
下面是一些示例代码：
Pattern pattern = Pattern.compile("THE (REGEX) (EXPRESSION) (WITH MULTIPLE) GROUPS");
Matcher matcher = pattern.matcher("THE TEXT TO SEARCH AND MODIFY");
StringBuffer buffer = new StringBuffer();
while(matcher.find()){
matcher.appendReplacement(buffer, processTheGroup(matcher.group(3));
}
but I would like to do something like this (obviously this doesn't work).
但我想做这样的事情（显然这行不通）。
...
while(matcher.find()){
matcher.group(3).appendReplacement(buffer, processTheGroup(matcher.group(3));
}
Something like that, where it only replaces a certain group, not the whole Pattern.
类似的东西，它只替换某个组，而不是整个 Pattern。
EDIT: changed the regex example to show that not all of the pattern is grouped.
编辑：更改了正则表达式示例以显示并非所有模式都已分组。
采纳答案by polygenelubricants
Let's say your entire pattern matches "(prefix)(infix)(suffix)", capturing the 3 parts into groups 1, 2 and 3 respectively. Now let's say you want to replace only group 2 (the infix), leaving the prefix and suffix intact the way they were.
假设您的整个模式匹配"(prefix)(infix)(suffix)"，分别将 3 个部分捕获到组 1、2 和 3 中。现在假设您只想替换第 2 组（中缀），保持前缀和后缀保持原样。
Then what you do is you append what group(1)matched (unaltered), the new replacement for group(2), and what group(3)matched (unaltered), so something like this:
然后你要做的是附加group(1)匹配的（未改变的），新的替换group(2)，以及group(3)匹配的（未改变的），所以是这样的：
matcher.appendReplacement(
buffer,
matcher.group(1) + processTheGroup(matcher.group(2)) + matcher.group(3)
);
This will still match and replace the entire pattern, but since groups 1 and 3 are left untouched, effectively only the infix is replaced.
这仍将匹配并替换整个模式，但由于组 1 和 3 保持不变，因此实际上只替换了中缀。
You should be able to adapt the same basic technique for your particular scenario.
您应该能够为您的特定场景调整相同的基本技术。
回答by Warren
I see this already has an accepted answer, but it is not fully correct. The correct answer appears to be something like this:
我看到这已经有一个公认的答案，但它并不完全正确。正确答案似乎是这样的：
.appendReplacement("" + process(m.group(2)) + "");
This also illustrates that "$" is a special character in .appendReplacement. Therefore you must take care in your "process()" function to replace all "$" with "\$". Matcher.quoteReplacement(replacementString) will do this for you (thanks @Med)
这也说明“$”是 .appendReplacement 中的一个特殊字符。因此，您必须小心使用“process()”函数将所有“$”替换为“\$”。Matcher.quoteReplacement(replacementString) 会为你做这件事（感谢@Med）
The previous accepted answer will fail if either groups 1 or 3 happen to contain a "$". You'll end up with "java.lang.IllegalArgumentException: Illegal group reference"
如果第 1 组或第 3 组碰巧包含“$”，则先前接受的答案将失败。你最终会得到“java.lang.IllegalArgumentException: Illegal group reference”
