docs: public static void main(String[] args)
      throws IOException, NoSuchAlgorithmException, InvalidKeyException, XmlPullParserException {
      try {
        /* play.min.io for test and development. */
        MinioClient minioClient = new MinioClient("https://play.min.io:9000", "Q3AM3UQ867SPQQA43P2F",
                                                  "zuf+tfteSlswRu7BJ86wekitnifILbZam1KYY3TG");
  
        /* Amazon S3: */
        // MinioClient minioClient = new MinioClient("https://s3.amazonaws.com", "YOUR-ACCESSKEYID",
        //                                           "YOUR-SECRETACCESSKEY");
  
        // Create new PostPolicy object for 'my-bucketname', 'my-objectname' and 7 days expire time from now.
        PostPolicy policy = new PostPolicy("my-bucketname", "my-objectname", DateTime.now().plusDays(7));
        // 'my-objectname' should be 'image/png' content type
        policy.setContentType("image/png");
        Map<String,String> formData = minioClient.presignedPostPolicy(policy);
  
        // Print a curl command that can be executable with the file /tmp/userpic.png and the file will be uploaded.
        System.out.print("curl -X POST ");
        for (Map.Entry<String,String> entry : formData.entrySet()) {
          System.out.print(" -F " + entry.getKey() + "=" + entry.getValue());
        }
        System.out.println(" -F file=@/tmp/userpic.png https://play.min.io:9000/my-bucketname");
      } catch (MinioException e) {
        System.out.println("Error occurred: " + e);
      }
    }