请将给出的罗马数字转化为整数
保证输入的数字范围在1 到 3999之间。

Given a roman numeral, convert it to an integer.
Input is guaranteed to be within the range from 1 to 3999.

这道题会有点乱，不够简化

public static int romanToInt (String s) {
        int ans=0;
        boolean sign = false;
        char[] array = s.toCharArray();//把他拆成数组
        int[] sn = new int[]{1,4,5,9,10,40,50,90,100,400,500,900,1000};
        String[] st=new String[]{"I","IV","V","IX","X","XL","L","XC","C","CD","D","CM","M"};//两个比对的数组
        for(int i =0;i<array.length;i++){ 
            sign = false;
            StringBuffer sb = new StringBuffer();
            if(i<array.length-1){
                sb.append(array[i]);
                sb.append(array[i+1]);
                for(int j =st.length-1;j>=0;j--){
                    if(st[j].equals(sb.toString())){
                        ans+=sn[j];
                        sign=true;
                        i++;break;
                    }
                }
            }//先判断是否构成两个数字的罗马文字
            if(!sign){
                for(int j =st.length-1;j>=0;j--){
                    String value = new String(""+array[i]);
                    if(st[j].equals(value)){
                        ans+=sn[j]; //单个文字就直接给加上ans
                        break;
                    }
                }
            }
    System.out.println(ans);
        }

        return ans;
    }