How to extract and replace a particular pattern from string using regex?

Question

I know this question has been asked many times on Stack Overflow but regex is too hard to understand.

What I tried:

String sentence = "The #{adjective} brown fox jumps over the lazy dog";
            String requierd_sentence = sentence.replaceAll("[{*.*}]", "quick");
            System.out.println(requierd_sentence);

Here in this sentence, adjectives are not at fixed position — they change with every new string/sentence. What I need to do is, replace the adjective with required string which is available in another column besides the sentence column. So fetching the string from column is OK, but regex matching is failing on many attempts.

What would be the correct regex for #{any string}?

Sample output for above string would be = The quick brown fox jumps over the lazy dog.
Another example input, All that #{adjective} is not gold should output All that glitters is not gold.

Now both sentences above have #{adjective} on different positions of the sentence, so I can't use split. I have to use a regex pattern.

Give sample input and output. It would make more sense than multiline explainations of the output expected. — TheLostMind
– TheLostMind, Commented Jun 17, 2014 at 5:22
Properly escape the [ and {: sentence.replaceAll("\\[\\{*.*}]", "quick");. — Amal
– Amal, Commented Jun 17, 2014 at 5:23

zx81 · Accepted Answer · 2014-06-17 05:40:59Z

2

You can use this (see demo):

String replaced = your_original_string.replaceAll("#\\{[^}]*}", "quick");

How Does This Work?

The #\\{ matches the literal characters *{
The [^}]* negative character class matches any characters that are not a closing brace
The } matches a closing brace
We replace all of this with "quick"

edited Jun 17, 2014 at 5:40

answered Jun 17, 2014 at 5:28

zx81

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3 Comments

paul Over a year ago

Superb! it worked, but explanation is not good. However, 3 cheers for the spirit, that you cared to give just not the answer but explanation also, so that people can learn. Can you explain it in better way.

zx81 Over a year ago

@paul Completely rewrote the explanation. Does this work for you? Let me know. :)

paul Over a year ago

Thanks, understood. Upvote for demo, its an excellent thing to learn regex.

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