This paper describes a system called STeP_IN (standing for Socio-Technical Platform for in situ Networking) that assists software developer to find and learn Java API libraries. It provides individualized search interface for Java developers, examples that illustrates the usage, and more distinctively a facilitating mechanism that connects Java developers to exchange expertise based on their expertise and social relations. STeP_IN is designed and developed based on the Dynamic Community theory, a new collaboration form that we have proposed.