Image compression script using online service - TinyPNG

OptimizeImage.java

import java.io.InputStream;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.nio.file.StandardCopyOption;
import java.io.File;
import javax.xml.bind.DatatypeConverter;

public class OptimizeImage {
  private static final String API_URL = "https://api.tinify.com/shrink";
  private static int count = 0;
  private static final String output = "output.png";

  private static long initialSize = 0;

  public static void main(String[] args) throws Exception {

        if(args.length < 1){
            System.err.println("Not enough arguments");
            return;
        }

        final String input = args[0];
	
	checkInput(input);

        loop(input);
    }

    public static void checkInput(String input){
    
        File inputFile = new File(input);
        if(!inputFile.exists()){
            System.err.println("File doesnt exist");
            System.exit(1);
        }

        initialSize = inputFile.length();
        System.out.println("Initial size: " + size);
    } 

    public static void loop(String input) throws Exception {

        final String key = "api-key-here";

        HttpURLConnection connection = (HttpURLConnection) new URL(API_URL).openConnection();
        String auth = DatatypeConverter.printBase64Binary(("api:" + key).getBytes("UTF-8"));
        connection.setRequestProperty("Authorization", "Basic " + auth);
        connection.setDoOutput(true);

        try (OutputStream request = connection.getOutputStream()) {
           Files.copy(Paths.get(input), request);
        }

        if (connection.getResponseCode() == 201) {
           // Compression was successful, retrieve output from Location header.
           final String url = connection.getHeaderFields().get("Location").get(0);
           connection = (HttpURLConnection) new URL(url).openConnection();
           try (InputStream response = connection.getInputStream()) {
              Files.copy(response, Paths.get(output), StandardCopyOption.REPLACE_EXISTING);
           }

         long size = new File(output).length();
         System.out.println("Size: " + size);
    
         if(count < 4){
           count++;
           System.out.println("Completed cycle " + count);
           loop(output);
          }else{
           long diff = initialSize - size;
           System.out.println("Final compression - removed " + diff + " bytes");
          }

        } else {
          // Something went wrong! You can parse the JSON body for details.
         System.err.println("Compression failed.");
        }
    }
}