java - 如何在正则表达式的单行上进行匹配？

Question

我有一个正则表达式来匹配一行并将其删除。一切都在它下面(并将一切保持在它上面)。

Two Part Ask:

1) Why won't this pattern match the given String text below?
2) How can I be sure to just match on a single line and not multiple lines?
   - The pattern has to be found on the same single line.

    String text = "Keep this.\n\n\nPlease match junkhere this t-h-i-s is missing.\n"
            + "Everything should be deleted here but don't match this on this line" + "\n\n";
    Pattern p = Pattern.compile("^(Please(\\s)(match)(\\s)(.*?)\\sthis\\s(.*))$", Pattern.DOTALL );
    Matcher m = p.matcher(text);
    if (m.find()) {
        text = (m.replaceAll("")).replaceAll("[\n]+$", "");  // remove everything below at and below "Please match ... this"
        System.out.println(text);
    }

预期输出:

Keep this.

Answer 1

你让你的生活变得复杂了......

首先，正如我在评论中所说，使用 Pattern.MULTILINE。

然后，要从匹配的开头截断字符串，请使用 .substring():

final Pattern p = Pattern.compile("^Please\\s+match\\b.*?this",
    Pattern.MULTILINE);
final Matcher m = p.matcher(input);
return m.find() ? input.substring(0, m.start()) : input;