if (instructionList.isEmpty() || instructionList.getLast() != handle) instructionList.addLast(handle);
assert handle != getLastInstruction(); instructionList.add(handle);
    public void addInstruction(InstructionHandle handle) {	// Only add the instruction if it hasn't already been added.	if (instructionList.isEmpty() || instructionList.getLast() != handle)	    instructionList.addLast(handle);    }