How do you make an S3 object public via the aws Java SDK?

An alternative approach which allows for more finegrained control of who exactly is allowed to view the object (all users or authenticated users only):

    PutObjectRequest putObjectRequest = new PutObjectRequest(bucketName, keyName, image);
    AccessControlList acl = new AccessControlList();
    acl.grantPermission(GroupGrantee.AllUsers, Permission.Read); //all users or authenticated
    putObjectRequest.setAccessControlList(acl);
    s3client.putObject(putObjectRequest);

s3client.setObjectAcl("bucketName[/subDirectory]", fileName, CannedAccessControlList.PublicRead);
URL url = s3client.getUrl("bucketName[/subDirectory]", fileName);
String sharableLink = url.toExternalForm();

source

Found the answer in an amazon aws forum.

return s3Client.putObject(
   new PutObjectRequest(bucketName, objectKey, inputStream, metadata)
      .withCannedAcl(CannedAccessControlList.PublicRead));

The answer being

.withCannedAcl(CannedAccessControlList.PublicRead)