Java十进制转二进制

闲着没事写了个简单的十进制转二进制的算法，很简单，个人记录一下，不妥之处请指正。

public static String toBinaryString(int j) {
        if (j < 0) {
            throw new NumberFormatException("不支持负数");
        }
        double i = (double) j;
        StringBuilder sb = new StringBuilder();
        while (true) {
            if (i % 2 == 0)
                sb.append("0");
            else
                sb.append("1");
            int result = (int) (i / 2);
            if (result == 1) {
                sb.append("1");
                break;
            }
            i = (double) result;
        }
        char[] chars = sb.toString().toCharArray();
        int len = chars.length - 1;
        for (int a = 0; a <= len; a++) {
            char c = chars[a];
            char d = chars[len];
            chars[a] = d;
            chars[len] = c;
            len--;
        }
        return new String(chars);
    }