Why doesn't replaceAll work in this line of code?

Question

    String weatherLocation = weatherLoc[1].toString();
weatherLocation.replaceAll("how","");
weatherLocation.replaceAll("weather", "");
weatherLocation.replaceAll("like", "");
weatherLocation.replaceAll("in", "");
weatherLocation.replaceAll("at", "");
weatherLocation.replaceAll("around", "");
test.setText(weatherLocation);

weatherLocation still contains "like in"

Rohit Jain · Answer 1 · 2013-09-28T08:44:13.603

12

Strings are immutable. String#replaceAll() method will create a new string. You need to re-assign the result back to the variable:

weatherLocation = weatherLocation.replaceAll("how","");

Now, since the replaceAll method returns the modified string, you can also chain multiple replaceAll call in single line. In fact, you don't need a replaceAll() here. It is required, when you want to replace substring matching a regex pattern. Simply use String#replace() method:

weatherLocation = weatherLocation.replace("how","")
                                 .replace("weather", "")
                                 .replace("like", "");

edited Sep 28 '13 at 08:44

answered Jun 25 '13 at 11:39

Rohit Jain

209,639
45
409
525

6

Also, quite wrong :) – Ernest Friedman-Hill Jun 25 '13 at 11:40
i failed completely with my answer, yes -.- removed it. – luk2302 Jun 25 '13 at 11:41

score 6 · Answer 2 · answered Jun 25 '13 at 11:41

As Rohit Jain said, Strings are immutable; in your case you could chain calls to replaceAll to avoid multiple affectations.

String weatherLocation = weatherLoc[1].toString()
        .replaceAll("how","")
        .replaceAll("weather", "")
        .replaceAll("like", "")
        .replaceAll("in", "")
        .replaceAll("at", "")
        .replaceAll("around", "");
test.setText(weatherLocation);

score 2 · Answer 3 · answered Jun 25 '13 at 12:14

2

Exactly as Rohit Jain said, and also, since replaceAll takes regex, instead of chaining calls you can simply do something like

test.setText(weatherLocation.replaceAll("how|weather|like|in|at|around", ""));

answered Jun 25 '13 at 12:14

Sethiel

182
6
14

pepuch · Answer 4 · 2013-06-25T12:07:25.857

1

I think that better will be to use StringBuilder/StringBuffer if you need to replace a lot of strings in text. Why? As Rohit Jain wrote String is immutable so every call of replaceAll method needs to create new object. Unlike String, StringBuffer/StringBuilder are mutable so it won't create new object (it will work on the same object).

You can read about StringBuilder for example in this Oracle tutorial http://docs.oracle.com/javase/tutorial/java/data/buffers.html.

edited Jun 25 '13 at 12:07

answered Jun 25 '13 at 11:47

pepuch

6,346
7
51
84

The problem is that `StringBuffer`/`StringBuilder` don't have a `replaceAll` method. – Ahmed KRAIEM Jun 25 '13 at 12:07
Of course, you are right but it doesn't mean that you can't replace strings in StringBuffer/StringBuilder. You can use `replace` method. – pepuch Jun 25 '13 at 12:08
You can use http://stackoverflow.com/a/3472705/393487 – Ahmed KRAIEM Jun 25 '13 at 12:09

Why doesn't replaceAll work in this line of code?

4 Answers4

Linked

Related