Get all QC tests from test plan through OTAClient - JAVA

Which is the Interface used to access all the test cases in test plan in QC? For Test set details in Test lab we have ITestSetFactory. But how can we get all the test details from QC in some collection object in Key-Value pair?

The data retrieval is more crucial for now. Using OTAClient.dll converted in Java jar and using com4j as a bridge!

Thanks in advance!

ITDConnection QCConnection =null;
try{
  QCConnection = ClassFactory.createTDConnection();
  QCConnection.initConnection("QC URL", domain, domainPswd);
  IList domains = QCConnection.domainsList();
  IList projectList = QCConnection.projectsList();
  List<String> domainList = new ArrayList<String>();
  for(int i=1;i<domains.count();i++){
    domainList.add((String)domains.item(i));
    System.out.println("DOmains: "+domains.item(i));
  }
  for(int i=1;i<projectList.count();i++){
    System.out.println("Projects : "+projectList.item(i));
  }
  QCConnection.connectProject(project, "LoginName", "Password");
  ITreeManager iTreeManager = QCConnection.treeManager().queryInterface(ITreeManager.class);
  ISubjectNode iSubNode = iTreeManager.nodeByPath("Subject").queryInterface(ISubjectNode.class);

  IList testFolders = iSubNode.newList();
  for(Com4jObject isys:testFolders){
    System.out.println("Test folder : "+isys.queryInterface(ISysTreeNode.class).name());
  }
}
catch(Exception e){
  System.out.println("Exceptions occured: "+e.getMessage());
}

Will Display all the folders in the project!