public static void minus(String s1, String s2) {
        boolean flag = true;// true:有負號，false:無負號（表示結果）
        if (s1.length() > s2.length()) {// s1>s2
            flag = false;
        }
        if (s1.length() == s2.length()) {//
            for (int i = 0; i < s1.length(); i++) {
                if
 
 (s1.charAt(i) > s2.charAt(i)) {
                    flag = false;
                    break;
                } else if (s1.charAt(i) < s2.charAt(i)) {
                    break;
                }
            }
        }
        int[] x;
        int i = 0, j = 0;
        if (flag) {// s1<s2
            j = s2.length() - s1.length();
            x = new
 
 int[s2.length()];
            i = 0;
            while (i < j) {
                x[i] = Integer.parseInt(String.valueOf(s2.charAt(i)));
                i++;
            }
            int ii = s2.length() - 1, jj = s1.length() - 1;
            for (; jj >= 0; ii--, jj--) {
                int t1 = Integer.parseInt(String.valueOf(s2.charAt(ii)));
                int
 
 t2 = Integer.parseInt(String.valueOf(s1.charAt(jj)));
                x[ii] = t1 - t2;
            }

        } else {
            j = s1.length() - s2.length();
            i = 0;
            x = new int[s1.length()];
            while (i < j) {
                x[i++] = Integer.parseInt(String.valueOf(s1.charAt(i)));
            }
            int ii = s1.length() - 1, jj = s2.length() - 1;
            for (; jj >= 0; ii--, jj--) {
                int t1 = Integer.parseInt(String.valueOf(s1.charAt(ii)));
                int t2 = Integer.parseInt(String.valueOf(s2.charAt(jj)));
                x[ii] = t1 - t2;
            }
        }
        // 處理由於不夠減產生負數的情況
        // System.out.println(Arrays.toString(x));
        for (int ii = x.length - 1; ii > 0; ii--) {
            if (x[ii] < 0) {
                x[ii - 1] = x[ii - 1] - 1;
                x[ii] += 10;
            }
        }

        String res = new String();
        if (flag) {
            res += '-';
        }
        for (i = 0; i < x.length; i++) {// 去掉計算中產生的0（最前面）
            if (x[i] != 0) {
                break;
            }
        }
        for (; i < x.length; i++) {
            res += x[i];
        }
        System.out.println("減法結果：" + res);

    }