Find markdown image syntax in String in Java

Question

I've a long text in Java, which contains at least one markdown image syntax. If there're N markdown image syntax, I will need to split the string into N+1 substrings and store them in an array of String, call texts. For example, I've the following text

Hello world!
![Alt text](/1/2/3.jpg)
Hello Stack Overflow!

Then Hello world!\n will be stored in position 0 and \nHello Stack Overflow! will be stored in position 1. For my question, we can assume that

The Alt text part contains only character A-Z, a-z and blank space.
The URL part contains only digits 0-9 and slash /. Its extension will only be .jpg. Other extension will not exist.

My question is how to split the text ? Do we need a java regular expression, such as *![*](*.jpg) ?

A regex, sure - why not. Is your regex notation different than the standard one? — Jongware
– Jongware, Commented Apr 3, 2016 at 22:27
No, my regex notation supposes to be same as the standard one. If there's error, it's my fault. (I don't know much about regular expression) — Mincong Huang
– Mincong Huang, Commented Apr 3, 2016 at 22:29

Community · Accepted Answer · 2017-05-23 12:02:11Z

11

Try this (ready to copy-paste):

"!\\[[^\\]]+\\]\\([^)]+\\)"

See here for info about how to get the matches.

"Untainted" version: !\[[^\]]+\]\([^)]+\)

Explanation

! literally !
\[ escaped [
[^\]]+ as many not ]s as possible
\]\( escaped ](
[^)]+ as many not )s as possible
\) escaped )

edited May 23, 2017 at 12:02

CommunityBot

11 silver badge

answered Apr 3, 2016 at 23:26

Laurel

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3 Comments

Laurel Over a year ago

@MincongHuang Added! I explained the "untainted" version.

Mincong Huang Over a year ago

Wonderful explanation. I've learnt a lot from it, thank you @Laurel

Mincong Huang Over a year ago

Actually, the escaped content (markdown) are useful for me. Can I get them and put them into other string array ?

Ying Yi · Accepted Answer · 2017-06-14 06:47:16Z

This is my way

public class Test {

public static void main(String[] args) {
    // TODO Auto-generated method stub
     List<String> allMatches = new ArrayList<String>();
     String str = "}```![imageName](/sword?SwordControllerName=KMFileDownloadController&id=c60b6c5a8d9b46baa1dc266910db462d \"imageName\")#### JSON data";
     Matcher m = Pattern.compile("\\[.*\\]\\((.*)\\)").matcher(str);
     while (m.find()) {
         allMatches.add(m.group(1).split(" ")[0]);
     }
     //print "/sword?SwordControllerName=KMFileDownloadController&id=c60b6c5a8d9b46baa1dc266910db462d"
     for(String s:allMatches){
         System.out.println(s);
     }
  }
}

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions

Juergen Schulze · Accepted Answer · 2018-05-08 12:32:59Z

0

!\[[^\]]*?\]\([^)]+\)

That way Alt Text can stay empty - though it makes no sense

answered May 8, 2018 at 12:32

Juergen Schulze

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