JAVA: subclasses, self-learning-test, coursework, homework

Answer 1

The way the assignment is leaning, it appears you're supposed to subclass Instruction - forex:

public class AddInstruction implements Instruction{

    public AddInstruction(String l, int r, int s1, int s2) {
        // Store the stuff passed in
    }

    public void execute(Machine m) {
        Registers reg = m.getRegisters();
        reg.setRegister(r, reg.getRegister(s1) + reg.getRegister(s2));
    }
}