In a processor system comprising of a processor having an instruction decoder 22, a general register 61 composed of a plurality of register areas and at least one ALU 60, and a Java accelerator 30 for converting a Java bytecode sequence to a native instruction sequence for the processor and supplying the native instruction sequence to the instruction decoder. The Java accelerator 30 is composed of a bytecode translator 40 for converting the Java bytecode sequence to the native instruction sequence for the processor and a register status control unit 50 for mapping a Java operand stack to any of the register areas of the general register and detecting a bytecode redundant for the processor. When a redundant bytecode is detected by the register status control unit 50, the supply of the native instruction from the bytecode translator 40 to the instruction decoder 22 is inhibited.