Despite recent developments in higher-level middleware for the Grid supporting high level of ease-of-programming, hurdles for widespread adoption of Grids remain high, due to (1) assumption of peer-to-peer connectivity of all Grid nodes, as well as (2) lack of scalable programming and deployment support. We propose a Java-based programming environment for a hierarchically organized Grid named Jojo, that allow seamless utilization of privately addressed clusters. Jojo provides several features, including secure private remote invocation using Globus GRAM and ssh/rsh to privately addressed nodes in clusters, intuitive message passing API suitable for overlapped execution using multiple threads, and automatic user/system program staging. Using Jojo, users can easily construct and execute parallel distributed applications on the Grid. We show the design and implementation of its programming API, a working example, as well as preliminary performance evaluation results that prove the effectiveness of hierarchal execution.