A java downloader for all AppleTV Wallpapers (according to https://aerial-screensavers.netlify.com/). With the ability to resume the download if it gets interupted/stopped (just rerun the program). Using java.nio and parallel streams (for the flex).

AerialScreensaverDownloader.java

import java.io.File;
import java.io.FileOutputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.nio.channels.Channels;
import java.util.regex.MatchResult;
import java.util.regex.Pattern;
import java.util.stream.Collectors;

public class AerialScreensaverDownloader {
  private static final File BASE_DIR = new File("C:/tmp/aerial-screensavers/");

  public static void main(String[] args) throws Exception {
    String htmlContent;
    try (var urlStream = new URL("https://aerial-screensavers.netlify.com/").openStream()) {
      htmlContent = new String(urlStream.readAllBytes());
    }
    Pattern.compile("(http[\\w\\d:/.-]+?\\.mov)")
        .matcher(htmlContent)
        .results()
        .map(MatchResult::group)
        .collect(Collectors.toList()) // otherwise the stream does not appear to be parallel
        .parallelStream()
        .forEach(AerialScreensaverDownloader::saveResumable);
  }

  public static void saveResumable(String urlString) {
    try {
      var url = new URL(urlString.replaceFirst("https", "http")); // the certificate is not trusted by java
      var outputFile = new File(BASE_DIR, urlString.substring(urlString.lastIndexOf("/")));

      var httpConnectionForContentLength = (HttpURLConnection) url.openConnection();
      httpConnectionForContentLength.setRequestMethod("HEAD");
      var contentLength = httpConnectionForContentLength.getContentLengthLong();
      var fileLength = outputFile.length();

      var append = fileLength < contentLength;
      var httpConnection = (HttpURLConnection) url.openConnection();
      if(append) {
        httpConnection.setRequestProperty("Range", "bytes=" + fileLength + "-" + contentLength); // only download missing bytes
      } else if (fileLength == contentLength) return;

      try(var urlStream = httpConnection.getInputStream();
          var readableByteChannel = Channels.newChannel(urlStream);
          var fileOutputStream = new FileOutputStream(outputFile, append);
          var fileChannel = fileOutputStream.getChannel();) {
        fileChannel.transferFrom(readableByteChannel, fileLength, Long.MAX_VALUE);
      } catch (Exception e) {
        e.printStackTrace();
      }
    } catch (Exception e) {
      e.printStackTrace();
    }
  }

}