How to replace a substring of a string [duplicate]

Question

Assuming I have a String string like this:

"abcd=0; efgh=1"

and I want to replace "abcd" by "dddd". I have tried to do such thing:

string.replaceAll("abcd","dddd");

It does not work. Any suggestions?

EDIT: To be more specific, I am working in Java and I am trying to parse the HTML document, concretely the content between <script> tags. I have already found a way how to parse this content into a string:

 if(tag instanceof ScriptTag){
        if(((ScriptTag) tag).getStringText().contains("DataVideo")){
            String tagText = ((ScriptTag)tag).getStringText();
      }
}

Now I have to find a way how to replace one substring by another one.

Can you be more specific than "it does not work?" First of all, what language is this? Do you get an error? Does something unexpected happen? What are you trying to accomplish in general? — Explosion Pills
– Explosion Pills, Commented May 22, 2013 at 22:05

Andrii Omelchenko · Accepted Answer · 2019-01-16 14:12:34Z

88

You need to use return value of replaceAll() method. replaceAll() does not replace the characters in the current string, it returns a new string with replacement.

String objects are immutable, their values cannot be changed after they are created.

You may use replace() instead of replaceAll() if you don't need regex.

    String str = "abcd=0; efgh=1";
    String replacedStr = str.replaceAll("abcd", "dddd");

    System.out.println(str);
    System.out.println(replacedStr);

outputs

abcd=0; efgh=1
dddd=0; efgh=1

edited Jan 16, 2019 at 14:12

Andrii Omelchenko

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answered May 22, 2013 at 22:09

Alper

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1 Comment

HoldOffHunger Over a year ago

Note that replaceAll expects a regular expression. Replace blank parens, "()", will produce a regex error, until you do proper escaping: str.replaceAll("\$\$", "");

anubhava · Accepted Answer · 2013-05-22 22:24:50Z

17

2 things you should note:

Strings in Java are immutable to so you need to store return value of thereplace method call in another String.
You don't really need a regex here, just a simple call to String#replace(String) will do the job.

So just use this code:

String replaced = string.replace("abcd", "dddd");

answered May 22, 2013 at 22:24

anubhava

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Comments

Tom · Accepted Answer · 2015-12-28 23:38:42Z

13

You need to create the variable to assign the new value to, like this:

String str = string.replaceAll("abcd","dddd");

edited Dec 28, 2015 at 23:38

Tom

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answered May 22, 2013 at 23:36

EddyR

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Comments

Ricardo Cacheira · Accepted Answer · 2013-05-22 22:08:04Z

9

By regex i think this is java, the method replaceAll() returns a new String with the substrings replaced, so try this:

String teste = "abcd=0; efgh=1";

String teste2 = teste.replaceAll("abcd", "dddd");

System.out.println(teste2);

Output:

dddd=0; efgh=1

answered May 22, 2013 at 22:08

Ricardo Cacheira

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Andrii Omelchenko · Accepted Answer · 2019-01-16 14:11:34Z

4

Note that backslashes (\) and dollar signs ($) in the replacement string may cause the results to be different than if it were being treated as a literal replacement string; see Matcher.replaceAll. Use Matcher.quoteReplacement(java.lang.String) to suppress the special meaning of these characters, if desired.

from javadoc.

edited Jan 16, 2019 at 14:11

Andrii Omelchenko

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answered Dec 1, 2014 at 8:18

Amr Lotfy

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Comments

Bwire · Accepted Answer · 2013-05-22 22:08:34Z

0

You are probably not assigning it after doing the replacement or replacing the wrong thing. Try :

String haystack = "abcd=0; efgh=1";
String result = haystack.replaceAll("abcd","dddd");

answered May 22, 2013 at 22:08

Bwire

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