MarkdownParse.java

//https://howtodoinjava.com/java/io/java-read-file-to-string-examples/

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.ArrayList;

public class MarkdownParse {

    public static ArrayList<String> getLinks(String markdown) {
        ArrayList<String> toReturn = new ArrayList<>();
        // find the next [, then find the ], then find the (, then read link upto next )
        int currentIndex = 0;
        while(currentIndex < markdown.length()) {
            if (markdown.indexOf("[", currentIndex)==-1 || 
                  markdown.indexOf("]", currentIndex)==-1 || 
                  markdown.indexOf("(", currentIndex)==-1 || 
                  markdown.indexOf(")", currentIndex)==-1 ) {
                break;
            }
            int openBracket = markdown.indexOf("[", currentIndex);
            int closeBracket = markdown.indexOf("]", openBracket);
            int openParen = markdown.indexOf("(", closeBracket);
            int closeParen = markdown.indexOf(")", openParen);
            if (!(markdown.indexOf("!",openBracket-2)==openBracket-1 && 
             !(markdown.indexOf("!",openBracket-3)==openBracket-2))) {
                toReturn.add(markdown.substring(openParen+1, closeParen));
            }
            currentIndex = closeParen + 1;
        }

        return toReturn;
    }


    public static void main(String[] args) throws IOException {
        Path fileName = Path.of(args[0]);
        String content = Files.readString(fileName);
        ArrayList<String> links = getLinks(content);
	    System.out.println(links);
    }
}