This shows how to upload a video using an HTTP request.

There are code snippets that are also available in java (and kotlin is pretty similar).

In order to see how to upload a video, go to https://developers.google.com/youtube/v3/code_samples/code_snippets, select Videos under Resource and insert under method.

If you then click on Show code and select JAVA at the top, you will get this example code:

/**
 * Sample Java code for youtube.videos.insert
 * See instructions for running these code samples locally:
 * https://developers.google.com/explorer-help/guides/code_samples#java
 */

import com.google.api.client.googleapis.javanet.GoogleNetHttpTransport;
import com.google.api.client.googleapis.json.GoogleJsonResponseException;
import com.google.api.client.http.InputStreamContent;
import com.google.api.client.http.javanet.NetHttpTransport;
import com.google.api.client.json.JsonFactory;
import com.google.api.client.json.jackson2.JacksonFactory;

import com.google.api.services.youtube.YouTube;
import com.google.api.services.youtube.model.Video;
import com.google.api.services.youtube.model.VideoSnippet;
import com.google.api.services.youtube.model.VideoStatus;

import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.security.GeneralSecurityException;
import java.util.Arrays;
import java.util.Collection;

public class ApiExample {
    // You need to set this value for your code to compile.
    // For example: ... DEVELOPER_KEY = "YOUR ACTUAL KEY";
    private static final String DEVELOPER_KEY = "YOUR_API_KEY";

    private static final String APPLICATION_NAME = "API code samples";
    private static final JsonFactory JSON_FACTORY = JacksonFactory.getDefaultInstance();

    /**
     * Build and return an authorized API client service.
     *
     * @return an authorized API client service
     * @throws GeneralSecurityException, IOException
     */
    public static YouTube getService() throws GeneralSecurityException, IOException {
        final NetHttpTransport httpTransport = GoogleNetHttpTransport.newTrustedTransport();
        return new YouTube.Builder(httpTransport, JSON_FACTORY, null)
            .setApplicationName(APPLICATION_NAME)
            .build();
    }

    /**
     * Call function to create API service object. Define and
     * execute API request. Print API response.
     *
     * @throws GeneralSecurityException, IOException, GoogleJsonResponseException
     */
    public static void main(String[] args)
        throws GeneralSecurityException, IOException, GoogleJsonResponseException {
        YouTube youtubeService = getService();
        
        // Define the Video object, which will be uploaded as the request body.
        Video video = new Video();
        
        // Add the snippet object property to the Video object.
        VideoSnippet snippet = new VideoSnippet();
        snippet.setCategoryId("22");
        snippet.setDescription("Description of uploaded video.");
        snippet.setTitle("Test video upload.");
        video.setSnippet(snippet);
        
        // Add the status object property to the Video object.
        VideoStatus status = new VideoStatus();
        status.setPrivacyStatus("private");
        video.setStatus(status);

        // TODO: For this request to work, you must replace "YOUR_FILE"
        //       with a pointer to the actual file you are uploading.
        //       The maximum file size for this operation is 137438953472.
        File mediaFile = new File("YOUR_FILE");
        InputStreamContent mediaContent =
            new InputStreamContent("application/octet-stream",
                new BufferedInputStream(new FileInputStream(mediaFile)));
        mediaContent.setLength(mediaFile.length());

        // Define and execute the API request
        YouTube.Videos.Insert request = youtubeService.videos()
            .insert("snippet,status", video, mediaContent);
        Video response = request.setKey(DEVELOPER_KEY).execute();
        System.out.println(response);
    }
}

You can also look at another example java code for uploading a video to YouTube on GitHub.

Note that you will need to make a few changes to this:

Under Android, you don't have a main. You will need to (1) put that code whereever you need to and you might want to (2) do it asynchronously.

When using Kotlin, you will also (3) need to modify the syntax accordingly.

did you check the Youtube API on google developers guide, check the Video Upload section? you will find something like this:

VideoEntry newEntry = new VideoEntry();

YouTubeMediaGroup mg = newEntry.getOrCreateMediaGroup();
mg.setTitle(new MediaTitle());
mg.getTitle().setPlainTextContent("My Test Movie");
mg.addCategory(new MediaCategory(YouTubeNamespace.CATEGORY_SCHEME, "Autos"));
mg.setKeywords(new MediaKeywords());
mg.getKeywords().addKeyword("cars");
mg.getKeywords().addKeyword("funny");
mg.setDescription(new MediaDescription());
mg.getDescription().setPlainTextContent("My description");
mg.setPrivate(false);
mg.addCategory(new MediaCategory(YouTubeNamespace.DEVELOPER_TAG_SCHEME, "mydevtag"));
mg.addCategory(new MediaCategory(YouTubeNamespace.DEVELOPER_TAG_SCHEME, "anotherdevtag"));

newEntry.setGeoCoordinates(new GeoRssWhere(37.0,-122.0));
// alternatively, one could specify just a descriptive string
// newEntry.setLocation("Mountain View, CA");

MediaFileSource ms = new MediaFileSource(new File("file.mov"), "video/quicktime");
newEntry.setMediaSource(ms);

String uploadUrl =
  "http://uploads.gdata.youtube.com/feeds/api/users/default/uploads";

VideoEntry createdEntry = service.insert(new URL(uploadUrl), newEntry);

Probably you will the successfully authenticate before you can upload teh video like:

YouTubeService service = new YouTubeService(clientID, developer_key);

Hope this helps