microsoft-azure-storage/src/com/microsoft/azure/storage/file/CloudFile.java
@DoesServiceRequest
    public FileOutputStream openWriteExisting(AccessCondition accessCondition, FileRequestOptions options,
            OperationContext opContext) throws StorageException, URISyntaxException {
        return this.openOutputStreamInternal(null /* length */, accessCondition, options, opContext);
    }
@DoesServiceRequest
    public FileOutputStream openWriteExisting(AccessCondition accessCondition, FileRequestOptions options,
            OperationContext opContext) throws StorageException, URISyntaxException {
        return this.openOutputStreamInternal(null /* length */, accessCondition, options, opContext);
    }
Opens an output stream object to write data to the file, using specified request options and
operation context. The file must already exist and any existing data may be overwritten.

@param accessCondition
An {@link AccessCondition} object which represents the access conditions for the file.
@param options
A {@link FileRequestOptions} object that specifies any additional options for the request. Specifying
<code>null</code> will use the default request options from the associated service client (
{@link CloudFileClient}).
@param opContext
An {@link OperationContext} object which represents the context for the current operation. This object
is used to track requests to the storage service, and to provide additional runtime information about
the operation.

@return A {@link FileOutputStream} object used to write data to the file.

@throws StorageException
If a storage service error occurred.
@throws URISyntaxException