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()) {
            int openBracket = markdown.indexOf("[", currentIndex);
            if(openBracket < 0) break;

            int closeBracket = markdown.indexOf("]", openBracket);
            if(closeBracket < 0) break;

            int openParen = markdown.indexOf("(", closeBracket);
            if(openParen < 0) break;

            int closeParen = markdown.indexOf(")", openParen);
            if(closeParen < 0) break;

            String link = markdown.substring(openParen + 1, closeParen);
            currentIndex = closeParen + 1;

            if(link.indexOf(".") != -1 && link.indexOf(" ") == -1){
                // we found a link


            
                // make sure it is not image link:
                if(closeBracket < 0 || markdown.charAt(openBracket-1) == '!'){
                    continue;
                }
                toReturn.add(link);
            }

            else{
                
                while(link.indexOf(".") == -1 && link.indexOf(" ") == -1){
                    closeParen = markdown.indexOf(")", currentIndex);
                    if(closeParen < 0) break;
                    link = markdown.substring(openParen + 1, closeParen);
                    currentIndex = closeParen + 1;
                }

                if(link.indexOf(".") != -1 && link.indexOf(" ") == -1){
                    // we found a link
    
    
                
                    // make sure it is not image link:
                    if(closeBracket < 0 || markdown.charAt(openBracket-1) == '!'){
                        continue;
                    }
                    toReturn.add(link);
                }

            }
        }
        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);
    }
}