java - Why replaceAll is not working?
java, regex
Solution
The reason why it's not working: You need four backslashes in a Java string to create a single "real" backslash.
string = string.replaceAll(sc, "\\\\" + sc);
should work. But this is not the right way to do it. You don't need a `for` loop at all:
String string = "Hel%l&+++o_Wor_++l%d&#";
string = string.replaceAll("[%&_]", "\\\\$0");
and you're done.
Explanation:
- `[%&_]` matches any of the three characters you want to replace
- `$0` is the result of the match, so
- `"\\\\$0"` means "a backslash plus whatever was matched by the regex".
Caveat: This solution is obviously not checking whether any of those characters had already been escaped previously. So
Hello\%
would become
Hello\\%
which you would not want to happen. Could this be a problem?
Problem
Im starting to learn regex and I don't know if I understand it correctly. I have a problem with function replaceAll because it does not replace the character in a string that I want to replace. Here is my code: ``` public class TestingRegex { public static void main (String args[]) { String string = "Hel%l&+++o_Wor_++l%d&#"; char specialCharacters[] = {'%', '%', '&', '_'}; for (char sc : specialCharacters) { if (string.contains(sc + "")) string = string.replaceAll(sc + "", "\\" + sc); } System.out.println("New String: " + string); } } ``` The output is the same as the original. Nothing changed. I want the output to be : `Hel\%l\&+++o\_Wor\_++l\%d\&\#`. Please help. Thanks in advance.