Matching Line Boundaries in a Regular Expression
By default, the beginning-of-line matcher (^) and end-of-line matcher
($) do not match at line boundaries. They match the beginning and end
of the entire input sequence. For example, the pattern ^a matches
abc but does not match def\nabc. To enable ^ and
$ to match line boundaries, the pattern should be compiled with
the multiline flag enabled.
It is also possible to enable multiline mode within a pattern
using the inline modifier (?m). For example, multiline mode is
enabled in the pattern (?m)^a. Multiline mode can be disabled
using (?-m).
CharSequence inputStr = "abc\ndef";
String patternStr = "abc$";
// Compile with multiline enabled
Pattern pattern = Pattern.compile(patternStr, Pattern.MULTILINE);
Matcher matcher = pattern.matcher(inputStr);
boolean matchFound = matcher.find(); // true
// Use an inline modifier to enable multiline mode
matchFound = pattern.matches(".*abc$.*", "abc\r\ndef"); // false
matchFound = pattern.matches("(?m).*abc$.*", "abc\r\ndef"); // true
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