Using String's ReplaceAll with regex

Question

How to repalace the following String combination:
word1="word2"
With the following String combination:
word1="word3"

Using word boundaries \b.

I used the following, but did't work:

String word2 = "word2";
String word3 = "word3";
String oldLine = "word1=\"" + word2 + "\"";
String newLine = "word1=\"" + word3 + "\"";
String lineToReplace = "\\b" + oldLine + "\\b";
String changedCont = cont.replaceAll(lineToReplace, newLine);

Where cont is a String that contains a lot of characters including word1="word2" String combinations.

anubhava · Accepted Answer · 2025-03-03 19:54:13Z

2

If you replace your lineToReplace line by this:

String lineToReplace = "\\b" + oldLine + "(?!\\w)";

It should work the way you want.

By prefixing with \b we are making sure that there is a word boundary a the start.
By using negative lookahead (?!\w) we make sure that there is no word character on immediate right

edited Mar 3 at 19:54

answered Mar 12, 2012 at 13:34

anubhava

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3 Comments

Qtax Over a year ago

(?=\W|$) can also be written as (?!\w), or in this case just \B.

anubhava Over a year ago

Thanks @Qtax: Updated the answer with simpler (?!\\w).

Arvind Kumar Avinash Mar 2 at 14:07

It can be more useful if you explain what your pattern does.

Qtax · Accepted Answer · 2012-03-12 13:20:26Z

1

Remove the last \b. It will not do what you think, " is not a word character.

answered Mar 12, 2012 at 13:20

Qtax

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Comments

jabal · Accepted Answer · 2012-03-12 13:21:32Z

1

String input = "alma word1=\"word2\"";
String replacement = "word1=\"word3\"";
String output = input.replaceAll("\\bword1=\\\"word2\\\"", replaceMent);

answered Mar 12, 2012 at 13:21

jabal

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3 Comments

Bohemian Over a year ago

Double quotes are nothing special in regex, so you don't need to escape them - ie "\\bword1=\"word2\"" is preferable

GingerHead Over a year ago

@jabal jabal ma yehezzak ri7 :D

GingerHead Over a year ago

@jabal Sorry about that, but I thought you knew Arabic, where jabal in Arabic means mountain, and there's a famous proverb that says: "Oh mountain, never be shaken against any wind" ;-)

Mattias Isegran Bergander · Accepted Answer · 2012-03-12 13:51:30Z

1

You have word boundaries \b inside your string (the ") and you are using word boundaries in your regexp . Remove that last \b for example.

answered Mar 12, 2012 at 13:51

Mattias Isegran Bergander

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1 Comment

GingerHead Over a year ago

+1 for reminding me that I had a word boundaries \b inside my String already, which is the "

Bohemian · Accepted Answer · 2012-03-12 13:24:23Z

0

The only word boundary you need is at the front - the rest of your match already has word boundaries built in (the quotes etc).

This will work:

 cont.replaceAll("\\bword1=\"word2\"", "word1=\"word3\"");

answered Mar 12, 2012 at 13:24

Bohemian♦

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