Reconfigurable computing systems are devices where a CPU controls the system and uses a Field Programmable Gate Array (FPGA) for computationally intensive tasks.Whenever such a task is to be started, the FPGA can be reconfigured and instructed to start the calculation. Such communication is generally based on a message passing interface.As a new alternative we propose a portable and transparent interface between the Java Runtime Environment and a generic FPGA. From the software side, communication with hardware looks like regular method calls, while the hardware can access fields of Java objects, call methods, throw exceptions, etc.We feel this interface can ease hardware support for existing applications and allows development of new hardware supported applications in the object-oriented programming paradigm.