private static boolean isMultipartUploadETag(String eTag) {
        return eTag.contains("-");
    }
Returns true if the specified ETag was from a multipart upload.

@param eTag
           The ETag to test.
@return True if the specified ETag was from a multipart upload, otherwise false it if belongs
        to an object that was uploaded in a single part.
aws-java-sdk-s3/src/main/java/com/amazonaws/services/s3/internal/SkipMd5CheckStrategy.java