Replace all "?" with "\\?" in Java

Question

is it possible to replace all the questionmarks ("?") with "\?" ?

Lets say I have a String, and I want to delete some parts of that String, one part with an URL in it. Like this:

String longstring = "..."; //This is the long String
String replacestring = "http://test.com/awesomeness.asp?page=27";
longstring.replaceAll(replacestring, "");

But! As I understand it you can't use the replaceAll() method with a String that contains one single questionmark, you have to make them like this "\?" first.

So the question is; Is there some way to replace questionmarks with "\?" in a String? And no, I'm able to just change the String.

Thanks in advance, hope someone understands me! (Sorry for bad English...)

score 27 · Accepted Answer · answered Dec 09 '12 at 20:38

27

Don't use replaceAll(), use replace()!

It is a common misconception that replaceAll() replaces all occurrences and replace() just replaces one or something. This is totally incorrect.

replaceAll() is poorly named - it actually replaces a regex.
replace() replaces simple Strings, which is what you want.

Both methods replace all occurrences of the target.

Just do this:

longstring = longstring.replace(replacestring, "");

And it will all work.

answered Dec 09 '12 at 20:38

Bohemian

412,405
93
575
722

4

+1 for `common misconception` part. – Eng.Fouad Dec 09 '12 at 20:41
the javadoc indicates for replace(CharSequence, CharSequence): Replaces each substring of this string that matches the literal target sequence with the specified literal replacement sequence. – Elloco Jun 04 '18 at 12:15
@Elloco and your point is??? – Bohemian Jun 04 '18 at 15:00
I finally split the string by "?" and rebuild the string replacing "?"(s) I want ... – Elloco Jun 07 '18 at 07:33

PearsonArtPhoto · Answer 2 · 2012-12-09T21:07:43.900

4

Escape the \ too, using \\\\?.

String longstring = "..."; //This is the long String
String replacestring = "http://test.com/awesomeness.asp?page=27";
longstring=longstring.replaceAll(replacestring, "\\\\?");

But as other answer have mentioned, replaceAll is a bit overkill, just a replace should work.

edited Dec 09 '12 at 21:07

answered Dec 09 '12 at 20:32

PearsonArtPhoto

38,970
17
111
142

This actually works, but instead of "\\\?" you must have "\\\\?". But as Bohemian and the other guys said; I'll use replace() instead. Thanks anyway! – GuiceU Dec 09 '12 at 21:01

score 2 · Answer 3 · edited Oct 20 '16 at 19:33

2

Use String.replace() instead of String.replaceAll():

longstring = longstring.replace("?", "\\?");

String.replaceAll() uses Regular Expression, while String.replace() uses plain text.

edited Oct 20 '16 at 19:33

ccallendar

888
8
10

answered Dec 09 '12 at 20:32

Eng.Fouad

115,165
71
313
417

score 2 · Answer 4 · answered Dec 09 '12 at 20:32

2

replaceAll takes a regular expression, and ? has a special meaning in the regex world.

You should use replace in this case, since you don't need a regex.

String longstring = "..."; //This is the long String
String replacestring = "http://test.com/awesomeness.asp?page=27";
longstring = longstring.replace(replacestring, "");

Oh, and strings are immutable!! longstring = longstring.replace(..), notice the assignment.

answered Dec 09 '12 at 20:32

arshajii

127,459
24
238
287

String s = s.replace("?",null); – Umesh Bhutada Jun 09 '22 at 10:41

Replace all "?" with "\\?" in Java

4 Answers4