แปลงเลขฐาน n เป็นเลขฐาน 10

import java.util.Scanner;
 
public class Main {
    public static void main (String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.println(Integer.parseInt(scanner.nextLine(), n));
    }
}

import java.util.Scanner;
 
public class Main {
    public static void main (String[] args) {
        Scanner scanner = new Scanner(System.in);
        String text = scanner.nextLine();
 
        int base10Number = 0;
        int numberLength = text.length();
        for (int i = 0; i < numberLength; i++) {
            int num = Integer.parseInt(String.valueOf(text.charAt(i)));
            base10Number += (int) (num * Math.pow(2, numberLength - 1 - i));
        }
 
        System.out.println(base10Number);
    }
}

import java.util.Scanner;
 
public class Main {
    public static void main (String[] args) {
        Scanner scanner = new Scanner(System.in);
        String text = scanner.nextLine();
 
        int base10Number = 0;
        int numberLength = text.length();
        for (int i = 0; i < numberLength; i++) {
            int num = Integer.parseInt(String.valueOf(text.charAt(i)));
            base10Number += (int) (num * Math.pow(8, numberLength - 1 - i));
        }
 
        System.out.println(base10Number);
    }
}

import java.util.Scanner;
 
public class Main {
    public static void main (String[] args) {
        Scanner scanner = new Scanner(System.in);
        String text = scanner.nextLine();
 
        int base10Number = 0;
        int numberLength = text.length();
        for (int i = 0; i < numberLength; i++) {
 
            char numberChar = text.charAt(i);
            int number = switch (numberChar) {
                case 'A' -> 10;
                case 'B' -> 11;
                case 'C' -> 12;
                case 'D' -> 13;
                case 'E' -> 14;
                case 'F' -> 15;
                default -> Integer.parseInt(String.valueOf(numberChar));
            };
 
            base10Number += (int) (number * Math.pow(16, numberLength - 1 - i));
        }
 
        System.out.println(base10Number);
    }
}