existing stream to deliver and multiple files

I try to deliver new file or to update existing file from my repository workspace to existing Stream. I work snippets in plain java client.

I created a changeset and set comments and relate to workitem by creating new stream succesfully. But I try to deliver changeset to existing stream. I think I set to wrong streamConnection. I try like

IChangeSetHandle cs1 = workspace.createChangeSet(currentComponent, monitor);
SCMPlatform.getWorkspaceManager(workspace.teamRepository()).setComment(cs1, "comments", monitor);

IFolderHandle rootFolder = (IFolderHandle) workspace.configuration(currentComponent).rootFolderHandle(monitor);
String[] nameSegments = new String;
nameSegments = "project";
IVersionableHandle filePathHandle = workspace.configuration(currentComponent).resolvePath(rootFolder,nameSegments, monitor);

IFolderHandle projectFolder = (IFolderHandle) filePathHandle;

IFileItem file = (IFileItem) IFileItem.ITEM_TYPE.createItem();
file.setName("file2.txt");
file.setParent(projectFolder);//file.setParent(projectFolder);
IFileContentManager contentManager = FileSystemCore.getContentManager(repo);
IFileContent storedContent = contentManager.storeContent(IFileContent.ENCODING_US_ASCII,FileLineDelimiter.LINE_DELIMITER_PLATFORM,
new VersionedContentManagerByteArrayInputStreamPovider("The contents of mhhy file.txt".getBytes()), null, monitor);
file.setContentType(IFileItem.CONTENT_TYPE_TEXT);
file.setContent(storedContent);
file.setFileTimestamp(new Date());
workspace.commit(cs1, Collections
.singletonList(workspace.configurationOpFactory().save(file)), monitor);

IWorkItemClient workItemClient = (IWorkItemClient) repo.getClientLibrary(IWorkItemClient.class);
IWorkItemWorkingCopyManager copyManager = workItemClient.getWorkItemWorkingCopyManager();
IWorkItem workItem = workItemClient.findWorkItemById(972, IWorkItem.FULL_PROFILE, monitor);
IWorkItemHandle workItemhandle= workItemClient.findWorkItemById(972,IWorkItem.FULL_PROFILE, null);
.......
IChangeHistorySyncReport sync = workspace.compareTo(workspace, WorkspaceComparisonFlags.CHANGE_SET_COMPARISON_ONLY,
Collections.EMPTY_LIST, monitor);
workspace.deliver(workspace, sync, Collections.EMPTY_LIST,
sync.outgoingChangeSets(currentComponent), monitor);

I set to same values for StreamConnection and workspaceConnection because I want to deliver them to existing stream. Is it wrong or how can I set stream Connection? In addition it creates files in repository workspace.

And also I wonder about to deliver. Is it possible to deliver multiple files? I can do it like workspace.configurationOpFactory().save(rootFolder) ?