BASIC-11-十六进制转十进制-程序设计训练

问题描述

从键盘输入一个不超过8位的正的十六进制数字符串，将它转换为正的十进制数后输出。

注：十六进制数中的10~15分别用大写的英文字母A、B、C、D、E、F表示。

样例输入

FFFF

样例输出

65535

分析

本题不可以用integer自带的方法转,因为8个F会超出界限,报出NumberFormatException异常,所以需要用其他方法,本题思路,高位*16+低位,直到到个位

import java.math.BigInteger;
import java.util.Scanner;

public class Main {

    public static void main(String[] args) 
    {
            Scanner input = new Scanner(System.in);
            String str = input.next();
            String a[] = new String[str.length()];
            for (int i = 0; i < str.length(); i++) {
                switch (str.charAt(i)) {
                case "1":
                    a[i] = "1";
                    break;
                case "2":
                    a[i] = "2";
                    break;
                case "3":
                    a[i] = "3";
                    break;
                case "4":
                    a[i] = "4";
                    break;
                case "5":
                    a[i] = "5";
                    break;
                case "6":
                    a[i] = "6";
                    break;
                case "7":
                    a[i] = "7";
                    break;
                case "8":
                    a[i] = "8";
                    break;
                case "9":
                    a[i] = "9";
                    break;
                case "A":
                    a[i] = "10";
                    break;
                case "B":
                    a[i] = "11";
                    break;
                case "C":
                    a[i] = "12";
                    break;
                case "D":
                    a[i] = "13";
                    break;
                case "E":
                    a[i] = "14";
                    break;
                case "F":
                    a[i] = "15";
                    break;
                default:
                    a[i] = "0";
                    break;
                }

            }

            BigInteger bigInteger = new BigInteger(a[0]);
            BigInteger bigInteger2 = new BigInteger("16");
            for (int i = 1; i < a.length; i++) {
                bigInteger = bigInteger.multiply(bigInteger2).add(new BigInteger(a[i]));
            }

            System.out.println(bigInteger);

    }

}