java仿js的toString，无法解决精度问题，

toString.java

    @Test
    public void testRadix() {
        assertEquals("0.o72tt3lcjtq", toString("0.6721285152844136", 36));
    }
    public String toString(String number, int radix) {
        BigDecimal N = new BigDecimal(number);

        StringBuilder sb = new StringBuilder();
        BigInteger i = N.toBigInteger();
        sb.append(i.toString(radix));
        sb.append('.');
        while(new BigDecimal(N.intValue()).compareTo(N) != 0 && sb.length() < 13) {
            N = N.multiply(new BigDecimal(radix));
            i = N.toBigInteger().mod(new BigDecimal(radix).toBigInteger());
            sb.append(i.toString(radix));
        }
        return sb.toString();
    }