Java之实现十进制与十六进制转换案例讲解

import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;

public class Test {
    
    public static int covert(String content){
        int number=0;
        String [] HighLetter = {"A","B","C","D","E","F"};
        Map<String,Integer> map = new HashMap<>();
        for(int i = 0;i <= 9;i++){
            map.put(i+"",i);
        }
        for(int j= 10;j<HighLetter.length+10;j++){
            map.put(HighLetter[j-10],j);
        }
        String[]str = new String[content.length()];
        for(int i = 0; i < str.length; i++){
            str[i] = content.substring(i,i+1);
        }
        for(int i = 0; i < str.length; i++){
            number += map.get(str[i])*Math.pow(16,str.length-1-i);
        }
        return number;
    }
    //测试程序
    public static void main(String... args) {
        Scanner input = new Scanner(System.in);
        String content = input.nextLine();
        if(!content.matches("[0-9a-fA-F]*")){
            System.out.println("输入不匹配");
            System.exit(-1);
        }
        //将全部的小写转化为大写
        content = content.toUpperCase();
        System.out.println(covert(content));
    }

}

import java.util.Scanner;

public class Test2 {
    
    public static int  hexToDecimal(String hex){
        int outcome = 0;
        for(int i = 0; i < hex.length(); i++){
            char hexChar = hex.charAt(i);
            outcome = outcome * 16 + charToDecimal(hexChar);
        }
        return outcome;
    }
    
    public static int charToDecimal(char c){
        if(c >= 'A' && c <= 'F')
            return 10 + c - 'A';
        else
            return c - '0';
    }
    //测试程序
    public static void main(String... args) {
        Scanner input = new Scanner(System.in);
        String content = input.nextLine();
        if(!content.matches("[0-9a-fA-F]*")){
            System.out.println("输入不匹配");
            System.exit(-1);
        }
        //将全部的小写转化为大写
        content = content.toUpperCase();
        System.out.println(hexToDecimal(content));

    }
}