Sanity check on a Nexus 2 Maven Proxy repo

The task is: verify that all the JARs in a Nexus 2 repo are still in Maven Central.

I did a
find /path/to/nexusdata/central -name "*.jar" > alljarsfiltered.txt


and then run this Java application:

package mavenchecker;

import java.io.IOException;
import java.net.HttpURLConnection;
import java.net.URL;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.stream.Stream;

public class MavenChecker {
 public static ArrayList<String> errors = new ArrayList<String>();
 public static ArrayList<String> nonexisting = new ArrayList<String>();
 static int count  = 0;

 public static void main(String[] args) {

  String fileName = "/home/centos/Downloads/alljarsfiltered.txt";
  
  // read file into stream, try-with-resources
  try (Stream<String> stream = Files.lines(Paths.get(fileName)).parallel()) {

   stream.forEach((line) -> checkLine(line));
   

  } catch (IOException e) {
   e.printStackTrace();
  }

  for (String error : errors) {
   System.out.println("ERROR : " + error);
  }

  for (String nonexistingItem : nonexisting) {
   System.out.println("nonexisting : " + nonexistingItem);
  }

 }

 private static void checkLine(String line) {
  count++;
  if (count % 100 == 0) {
   System.out.println("COUNT " + count);
  }
  if (!line.endsWith(".jar"))
   return;

  String gavstring = line.replace("/path/to/nexusdata/central/", "");
  String[] parts = gavstring.split("/");
  int len = parts.length;
  if (len < 4) {
   System.err.println("invalid length for gavstring " + gavstring + " len = " + len + " should be at least 4");
   errors.add(gavstring);
  } else {
   String filename = parts[len - 1];
   String version = parts[len - 2];
   String artifactid = parts[len - 3];
   String group = String.join(".", Arrays.copyOfRange(parts, 0, len - 3));
   String message = "filename=" + filename + " group=" + group + " artifactid=" + artifactid + " version=" + version;
   //System.out.println(message);
   boolean exists = exists("https://repo.maven.apache.org/maven2/" + gavstring);
   if (!exists) nonexisting.add(gavstring);
   
   
  }

 }
 
 public static boolean exists(String URLName){
     try {
       HttpURLConnection.setFollowRedirects(false);
       // note : you may also need
       //        HttpURLConnection.setInstanceFollowRedirects(false)
       HttpURLConnection con =
          (HttpURLConnection) new URL(URLName).openConnection();
       con.setRequestMethod("HEAD");
       return (con.getResponseCode() == HttpURLConnection.HTTP_OK);
     }
     catch (Exception e) {
        e.printStackTrace();
        return false;
     }
   }

}