Ip總量計算工具

Ip總量計算工具

/**
 * <功能簡要> <br>
 * <ip段,ip總數計算工具>
 *
 * @Author heyanbo
 * @createTime 2020/5/6 23:15
 * @since 1.0
 */
public class IPTotalUtil {

    public static void main(String[] args) {
        Integer ipTotal = getIpTotal("192.168.0.1/20");
        System.out.println(ipTotal);
    }

    /**
     * 獲取ip段中的ip數量
     * 例:192.168.0.1/16
     * 計算公式： 2^(32-16)
     * @param cidr
     * @return
     */
    public static Integer getIpTotal(String cidr){
        String[] split = cidr.split("/");
        Integer num = Integer.valueOf(split[1]);
        return powerTwo(32 - num);
    }

    /**
     * 計算2的倍數
     * @param N
     * @return
     */
    public static int powerTwo(int N) {
        StringBuilder stringBuilder = new StringBuilder("");
        long num[] = new long[2];
        num[1] = 1;
        if (N > 62) {
            num[0] = 1;
            num[0] = num[0] << (N - 62);
            num[1] = num[1] << 62;
            String s = String.valueOf(num[1]);
            int size = 30, i = 0, j = 0;
            long n[] = new long[size + 1];
            for (i = s.length() - 1; i >= 0; --i) {
                n[j++] = (long) (num[0] * (s.charAt(i) - '0'));
            }
            for (i = 0; i < size; ++i) {
                while (n[i] > 9) {
                    n[i + 1] += n[i] / 10;
                    n[i] %= 10;
                }
            }
            boolean bl = false;
            for (i = size; i >= 0; --i) {
                if (n[i] != 0 || bl) {
                    stringBuilder.append(n[i]);
                    bl = true;
                }
            }
        } else {
            //左移運算符
            num[1] = num[1] << N;
            stringBuilder.append(String.valueOf(num[1]));
        }
        return Integer.valueOf(stringBuilder.toString());
    }
}