Java regex replaceAll multiline

java regex replaceall
Robert picture Robert · Nov 11, 2010 · Viewed 33.7k times · Source

I have a problem with the replaceAll for a multiline string:

String regex = "\\s*/\\*.*\\*/";
String testWorks = " /** this should be replaced **/ just text";
String testIllegal = " /** this should be replaced \n **/ just text";

testWorks.replaceAll(regex, "x"); 
testIllegal.replaceAll(regex, "x");

The above works for testWorks, but not for testIllegal!? Why is that and how can I overcome this? I need to replace something like a comment /* ... */ that spans multiple lines.

Answer

mikej picture mikej · Nov 11, 2010

You need to use the Pattern.DOTALL flag to say that the dot should match newlines. e.g.

Pattern.compile(regex, Pattern.DOTALL).matcher(testIllegal).replaceAll("x")

or alternatively specify the flag in the pattern using (?s) e.g. 

String regex = "(?s)\\s*/\\*.*\\*/";

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