HexString转Decimal（Int）异常：输入任意值结果均为0或1求解

我编写了三种基于数组实现十六进制字符串转十进制整数的Java代码，分别为if/else判断、字符串switch、字符字面量switch版本。核心逻辑是将十六进制字符串拆分为数组后从右到左遍历计算，但无论输入什么十六进制字符串，输出结果始终为0或1。先解决功能问题，代码冗长低效的问题后续再优化。

v1 - if/else测试版本（原代码） #

System.out.println("Enter a hexadecimal String to convert to decimal (base_10)");
while(true)
{
    System.out.print("Hexadecimal >> ");
    String hex = scan.nextLine();
    
    String hexArray[] = hex.split("");
    //int hexNum[] = new int[hexArray.length];
    
    //System.out.println(Arrays.toString(hexArray)); //test
    int sum = 0;
    int exp = 0;
    for (int i = hexArray.length-1; i > 0; i--)
    {
        if(hexArray[i].equalsIgnoreCase("A"))
            sum += 10 * Math.pow(16,exp);
        else if(hexArray[i].equalsIgnoreCase("B"))
            sum += 11 * Math.pow(16,exp);
        else if(hexArray[i].equalsIgnoreCase("C"))
            sum += 12 * Math.pow(16,exp);
        else if(hexArray[i].equalsIgnoreCase("D"))
            sum += 13 * Math.pow(16,exp);
        else if(hexArray[i].equalsIgnoreCase("E"))
            sum += 14 * Math.pow(16,exp);
        else if(hexArray[i].equalsIgnoreCase("F"))
            sum += 15 * Math.pow(16,exp);
        else
            sum += (Integer.parseInt(hexArray[i]) * Math.pow(16,exp));
        exp++;
    }
    System.out.println("\nHexadecimal: " + hex + "\t Decimal: " + sum);
}

问题点与修复 #

• 循环条件错误：i > 0会跳过数组索引0的字符（十六进制字符串的最高位），导致只计算了低位部分，修改为i >= 0才能遍历所有字符。
• Math.pow精度问题：Math.pow返回double类型，转换为int时可能出现精度丢失，改用整数累乘的方式替代。

修复后的代码：

import java.util.Scanner;

public class HexToDecimalIfElse {
    public static void main(String[] args) {
        System.out.println("Enter a hexadecimal String to convert to decimal (base_10)");
        Scanner scan = new Scanner(System.in);
        while(true)
        {
            System.out.print("Hexadecimal >> ");
            String hex = scan.nextLine().trim();
            if(hex.isEmpty()) continue;
            
            String hexArray[] = hex.split("");
            int sum = 0;
            int multiplier = 1; // 替代Math.pow，初始为16^0=1
            for (int i = hexArray.length-1; i >= 0; i--)
            {
                String ch = hexArray[i];
                int value;
                if(ch.equalsIgnoreCase("A"))
                    value = 10;
                else if(ch.equalsIgnoreCase("B"))
                    value = 11;
                else if(ch.equalsIgnoreCase("C"))
                    value = 12;
                else if(ch.equalsIgnoreCase("D"))
                    value = 13;
                else if(ch.equalsIgnoreCase("E"))
                    value = 14;
                else if(ch.equalsIgnoreCase("F"))
                    value = 15;
                else
                    value = Integer.parseInt(ch);
                sum += value * multiplier;
                multiplier *= 16; // 每次循环乘以16，对应下一位的权重
            }
            System.out.println("\nHexadecimal: " + hex + "\t Decimal: " + sum);
        }
    }
}

v2 - 字符串switch实现版本（原代码） #

System.out.println("Enter a hexadecimal String to convert to decimal (base_10)");
while(true)
{
    System.out.print("Hexadecimal >> ");
    String hex = scan.nextLine();
    
    String[] hexArray = hex.split("");
    
    System.out.println(Arrays.toString(hexArray)); //test
    int sum = 0;
    int exp = 0;
    for (int i = hexArray.length-1; i > 0; i--)
    {
        String s = hexArray[i];
        switch(s)
        {
            case "A":   case "a":
                 sum += (10 * Math.pow(16,exp));
                 break;
            case "B":   case "b":
                 sum += (11 * Math.pow(16,exp));
                 break;
            case "C":   case "c":
                 sum += (12 * Math.pow(16,exp));
                 break;
            case "D":   case "d":
                 sum += (13 * Math.pow(16,exp));
                 break;
            case "E":   case "e":
                 sum += (14 * Math.pow(16,exp));
                 break;
            case "F":   case "f":
                System.out.println("hi");
                 sum += (15 * Math.pow(16,exp));
                 break;
            default:    //i.e. NUMBERS
                 sum += ((Integer.parseInt(hexArray[i]) * Math.pow(16,exp)));
        }
        exp++;
    }
    System.out.println("\nHexadecimal: " + hex + "\t Decimal: " + sum);
    System.out.println("\n");
}

问题点与修复 #

同v1的两个核心问题：循环条件跳过首位、Math.pow精度问题，修复如下：

import java.util.Arrays;
import java.util.Scanner;

public class HexToDecimalStringSwitch {
    public static void main(String[] args) {
        System.out.println("Enter a hexadecimal String to convert to decimal (base_10)");
        Scanner scan = new Scanner(System.in);
        while(true)
        {
            System.out.print("Hexadecimal >> ");
            String hex = scan.nextLine().trim();
            if(hex.isEmpty()) continue;
            
            String[] hexArray = hex.split("");
            
            System.out.println(Arrays.toString(hexArray)); //test
            int sum = 0;
            int multiplier = 1;
            for (int i = hexArray.length-1; i >= 0; i--)
            {
                String s = hexArray[i];
                int value = 0;
                switch(s)
                {
                    case "A":   case "a":
                         value = 10;
                         break;
                    case "B":   case "b":
                         value = 11;
                         break;
                    case "C":   case "c":
                         value = 12;
                         break;
                    case "D":   case "d":
                         value = 13;
                         break;
                    case "E":   case "e":
                         value = 14;
                         break;
                    case "F":   case "f":
                        System.out.println("hi");
                         value = 15;
                         break;
                    default:    //i.e. NUMBERS
                         value = Integer.parseInt(hexArray[i]);
                }
                sum += value * multiplier;
                multiplier *= 16;
            }
            System.out.println("\nHexadecimal: " + hex + "\t Decimal: " + sum);
            System.out.println("\n");
        }
    }
}

v3 - 字符字面量switch实现版本（原代码） #

System.out.println("Enter a hexadecimal String to convert to decimal (base_10)");
while(true)
{
    System.out.print("Hexadecimal >> ");
    String hex = scan.nextLine();
    
    String[] hexArray = hex.split("");
    
    System.out.println(Arrays.toString(hexArray)); //test
    int sum = 0;
    int exp = 0;
    for (int i = hexArray.length-1; i > 0; i--)
    {
        char c = hexArray[i].charAt(0);
        switch(c)
        {
            case '0':
                break;
            case '1':
                sum += Math.pow(16,exp);
                break;
            case '2':
                sum += 2 * Math.pow(16,exp);
                break;
            case '3':
                sum += 3 * Math.pow(16,exp);
                break;
            case '4':
                sum += 4 * Math.pow(16,exp);
                break;
            case '5':
                sum += 5 * Math.pow(16,exp);
                break;
            case '6':
                sum += 6 * Math.pow(16,exp);
                break;
            case '7':
                sum += 7 * Math.pow(16,exp);
                break;
            case '8':
                sum += 8 * Math.pow(16,exp);
                break;
            case '9':
                sum += 9 * Math.pow(16,exp);
                break;
            case 'A':
            case 'a':
                sum += 10 * Math.pow(16,exp);
                break;
            case 'B':
            case 'b':
                sum += 11 * Math.pow(16,exp);
                break;
            case 'C':
            case 'c':
                sum += 12 * Math.pow(16,exp);
                break;
            case 'D':
            case 'd':
                sum += 13 * Math.pow(16,exp);
                break;
            case 'E':
            case 'e':
                sum += 14 * Math.pow(16,exp);
                break;
            case 'F':
            case 'f':
                sum += 15 * Math.pow(16,exp);
                break;
            default:
                ;   //Invalid Character
        }
        exp++;
    }
    System.out.println("\nHexadecimal: " + hex + "\t Decimal: " + sum);
}

问题点与修复 #

除循环条件和Math.pow的问题外，原代码中case '0'未处理数值累加（逻辑不完整），修复后：

import java.util.Arrays;
import java.util.Scanner;

public class HexToDecimalCharSwitch {
    public static void main(String[] args) {
        System.out.println("Enter a hexadecimal String to convert to decimal (base_10)");
        Scanner scan = new Scanner(System.in);
        while(true)
        {
            System.out.print("Hexadecimal >> ");
            String hex = scan.nextLine().trim();
            if(hex.isEmpty()) continue;
            
            String[] hexArray = hex.split("");
            
            System.out.println(Arrays.toString(hexArray)); //test
            int sum = 0;
            int multiplier = 1;
            for (int i = hexArray.length-1; i >= 0; i--)
            {
                char c = hexArray[i].charAt(0);
                int value = 0;
                switch(c)
                {
                    case '0':
                        value = 0;
                        break;
                    case '1':
                        value = 1;
                        break;
                    case '2':
                        value = 2;
                        break;
                    case '3':
                        value = 3;
                        break;
                    case '4':
                        value = 4;
                        break;
                    case '5':
                        value = 5;
                        break;
                    case '6':
                        value = 6;
                        break;
                    case '7':
                        value = 7;
                        break;
                    case '8':
                        value = 8;
                        break;
                    case '9':
                        value = 9;
                        break;
                    case 'A':
                    case 'a':
                        value = 10;
                        break;
                    case 'B':
                    case 'b':
                        value = 11;
                        break;
                    case 'C':
                    case 'c':
                        value = 12;
                        break;
                    case 'D':
                    case 'd':
                        value = 13;
                        break;
                    case 'E':
                    case 'e':
                        value = 14;
                        break;
                    case 'F':
                    case 'f':
                        value = 15;
                        break;
                    default:
                        value = 0; // 无效字符按0处理，也可抛出异常
                }
                sum += value * multiplier;
                multiplier *= 16;
            }
            System.out.println("\nHexadecimal: " + hex + "\t Decimal: " + sum);
        }
    }
}

内容的提问来源于stack exchange，提问作者Skelefish