题解 | #进制转换#

参考了“https://blog.nowcoder.net/n/7460061f61cd434991d8add0e2dac172?f=comment”。 改动了一下，

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String input = scanner.nextLine();
        scanner.close();
        if (input == null || input.length() < 3) {
            System.out.println("");
            return;
        }

        input = input.substring(2).toLowerCase();
        int len = input.length();
        int res = 0;
        for (int i = 0; i < len; i++) {
            char curChar = input.charAt(i);
            int curNum = 0;
            if (curChar >= '0' && curChar <= '9') {
                curNum = curChar - '0';
            } else if (curChar >= 'a' && curChar <= 'f') {
                curNum = curChar - 'a' + 10;
            } else {
                throw new RuntimeException("wrong input.");
            }
            res += curNum * Math.pow(16, len - i - 1);
        }
        System.out.println(res);
    }
}