RegEx從多行匹配到字符串緩沖區的末尾，並替換為“”

Question

我具有以下文件內容，並且嘗試匹配下面說明的reg，並將匹配項的開頭（“ On .... wrote”）替換為字符串緩沖區的末尾用空白“”：

-- file.txt (Before regx match and replace) -- 
test

On blah

more blah wrote:

So, this should be stripped all out and all that left should be the above test contents.
-- EOF -- 


-- file.txt (After regex mach and replace) -- 
test
-- EOF -- 

如果我從上方將文件內容讀取為字符串，然后嘗試匹配“ On ... wrote：”部分，則似乎無法從“ On ... writted：”替換文件末尾。 。：

    // String text = <file contents from above...the Before contents>
    Pattern PATTERN = 
      Pattern.compile("^(On\\s(.+)wrote:)$", Pattern.MULTILINE | Pattern.DOTALL );
    Matcher m = PATTERN.matcher(text);
    if (m.find()) {
       // This matches but I want to strip from "On....wrote:  -> <end of string>
       text = m.replaceAll("");  // This should only contain "test"

    }

Answer 1

您不需要進行比賽，就可以直接替換。 如果替換中使用的模式不匹配，則不會發生任何事情。

請嘗試以下操作：

// String text = <file contents from above...the Before contents>
String text = text.replaceAll("^(On.*?wrote:).*$", "");

注意：您可能需要從正則表達式內部打開Pattern.MULTILINE和Pattern.DOTALL的標志，您可以這樣操作：

String text = text.replaceAll("(?sm)^(On.*?wrote:).*$", "");

編輯：當然，您可以：

// String text = <file contents from above...the Before contents>
Pattern PATTERN = 
  Pattern.compile("^(On.*?wrote:).*$", Pattern.MULTILINE | Pattern.DOTALL );
Matcher m = PATTERN.matcher(text);
if (m.find()) {
   text = m.replaceAll("");  // This should only contain "test"

}