Modifying a webcrawler to search for keyword

I have to modify this webcrawler to search for a keyword. I've never worked with a webcrawler before so I'm completely lost. I've read over other codes and tried to understand them, but they don't match what I'm trying to accomplish. Any help? Thanks

public class Exercise12_33 {
public static void main(String[] args){
    java.util.Scanner input = new java.util.Scanner(System.in);
    System.out.print("Enter a URL: ");
    String url = input.nextLine();
    System.out.print("Enter a word to search: ");
    String keyword = input.nextLine();
    crawler(url, keyword); //Traverse the web from the a starting url
}

public static void crawler(String startingURL, String word){
    ArrayList<String> listOfPendingURLs = new ArrayList<>();
    ArrayList<String> listOfTraversedURLs = new ArrayList<>();

    listOfPendingURLs.add(startingURL);
    while (!listOfPendingURLs.isEmpty() &&
            listOfTraversedURLs.size() <= 100){
        String urlString = listOfPendingURLs.remove(0);
        if (!listOfTraversedURLs.contains(urlString)){
            listOfTraversedURLs.add(urlString);
            System.out.println("Craw " + urlString);

            for (String s: getSubURLs(urlString)){
                if (!listOfTraversedURLs.contains(s))
                    listOfPendingURLs.add(s);
            }
        }
    }
}

public static ArrayList<String> getSubURLs(String urlString){
    ArrayList<String> list = new ArrayList<>();

    try {
        java.net.URL url = new java.net.URL(urlString);
        Scanner input = new Scanner(url.openStream());
        int current = 0;
        while (input.hasNext()){
            String line = input.nextLine();
            current = line.indexOf("http:", current);
            while (current > 0) {
                int endIndex = line.indexOf("\"", current);
                if (endIndex > 0) {
                    list.add(line.substring(current, endIndex));
                    current = line.indexOf("http:", endIndex);
                }
                else
                    current = -1;
            }
        }
    }
    catch (Exception ex){
        System.out.println("Error: " + ex.getMessage());
        }
return list;
}

}