Hi Arun,
I am using the below method and getting a null pointer exception when I try to get itemId from build definition, although my work item id is correct.

public static void getBuildRequest(ITeamRepository repo) throws TeamRepositoryException {
        ITeamBuildClient buildClient = (ITeamBuildClient) repo.getClientLibrary(ITeamBuildClient.class);
        / The build definition is easy to get once you know the build ID /
        IBuildDefinition definition = buildClient.getBuildDefinition("313491", null);
        System.out.println("definition.getItemId(): "+ definition.getItemId());
        IBuildResultQueryModel buildResultQueryModel = IBuildResultQueryModel.ROOT;
        IItemQuery query = IItemQuery.FACTORY.newInstance(buildResultQueryModel);

        / Build up a query filter predicate that accepts a build definition as input to the query and checks for
           any non-personal builds that have a completed state. /
        IPredicate predicate = (buildResultQueryModel.buildDefinition()._eq(query.newItemHandleArg()))._and(
                buildResultQueryModel.personalBuild()._isFalse())._and(
                        buildResultQueryModel.buildState()._eq(BuildState.COMPLETED.name()));

        query.filter(predicate);

        / Order by build start time in descending order /
        query.orderByDsc(buildResultQueryModel.buildStartTime());

        / Query for items using the build definition's item ID as the argument. /
        / Use a smaller page size if possible depending on what is queried. /
        IItemQueryPage queryPage = buildClient.queryItems(query, new Object[] { definition.getItemId() },
                    IQueryService.ITEM_QUERY_MAX_PAGE_SIZE, null);

        / Iterate through the results of this page /

        while (queryPage.hasNext()) {
            queryPage = (IItemQueryPage) buildClient.fetchPage(queryPage.getToken(), queryPage.getNextStartPosition(), 1, null);
           
            / Iterate through each subsequent page. Break out of the loop if finished early. /
        }
    }

and here is the code that let me connect to repo

String repoUri = "https://xxxxx.eu.int:9443/jazz/";

        TeamPlatform.startup();
        try {
         
            // Login to the repository using the provided credentials
            if(TeamPlatform.getTeamRepositoryService() != null) {
          
            ITeamRepository repo = TeamPlatform.getTeamRepositoryService().getTeamRepository(repoUri);
            repo.registerLoginHandler(new ILoginHandler2() {
                @Override
                public ILoginInfo2 challenge(ITeamRepository repo) {
                    String userId = "jhhjkll3"; // Retrieve the userId in a secure way
                    String password = "kkk"; // Retrieve the password in a secure way
                    return new UsernameAndPasswordLoginInfo(userId, password);
                }
            });
           
            repo.login(null);
getBuildRequest(repo);