Lanqiao Cup Test Questions-Basic Practice Hexadecimal to Decimal

Resource limit
Time limit: 1.0s
Memory limit: 512.0MB

Problem description
Input a positive hexadecimal number string with no more than 8 digits from the keyboard, convert it to a positive decimal number and output it.
Note: 10~15 in hexadecimal numbers are represented by uppercase English letters A, B, C, D, E, and F respectively.

Sample input
FFFF
Sample output
65535

import java.util.*;
public class Main {
    
    	
	public static void main(String[] args) {
    
    
		Scanner sc = new Scanner(System.in);
		String str = sc.next();
		long ans=0;
		int  dig = str.length()-1;
		for(int i=0;i<str.length();i++){
    
    
			char c = str.charAt(i);
			int x = 0;
			switch(c){
    
    
			case '0': x = 0;break;
			case '1': x = 1;break;
			case '2': x = 2;break;
			case '3': x = 3;break;
			case '4': x = 4;break;
			case '5': x = 5;break;
			case '6': x = 6;break;
			case '7': x = 7;break;
			case '8': x = 8;break;
			case '9': x = 9;break;
			case 'A': x = 10;break;
			case 'B': x = 11;break;
			case 'C': x = 12;break;
			case 'D': x = 13;break;
			case 'E': x = 14;break;
			case 'F': x = 15;break;
			}
			ans = ans+x*((long)Math.pow(16, dig));
			dig--;
		}
		System.out.println(ans);
	}
}