zjzh/Main.java

import java.util.Scanner;

public class Main {

    // Helper function to convert a number from any base to decimal
    public static long convertToDecimal(String number, int base) {
        long result = 0;
        int power = 0;

        // Traverse the number from right to left
        for (int i = number.length() - 1; i >= 0; i--) {
            char digit = number.charAt(i);
            int value = 0;

            // Convert character to integer value
            if (Character.isDigit(digit)) {
                value = digit - '0';
            } else {
                value = Character.toUpperCase(digit) - 'A' + 10;
            }

            // Check if the value is within the allowed range for the given base
            if (value >= base) {
                throw new IllegalArgumentException("Invalid digit for the given base");
            }

            // Add the digit's value to the result
            result += value * Math.pow(base, power);
            power++;
        }

        return result;
    }

    // Helper function to convert a number from decimal to any base
    public static String convertFromDecimal(long number, int base) {
        if (number == 0) {
            return "0";
        }

        StringBuilder result = new StringBuilder();
        char[] digits = "0123456789ABCDEF".toCharArray();

        while (number > 0) {
            int remainder = (int) (number % base);
            result.insert(0, digits[remainder]);
            number /= base;
        }

        return result.toString();
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        // Input the number X in any base Rx
        System.out.print("输入数字X: ");
        String numberX = scanner.nextLine();
        System.out.print("Enter the base Rx (2-16): ");
        int baseX = scanner.nextInt();

        // Input the target base Ry
        System.out.print("Enter the target base Ry (2-16): ");
        int baseY = scanner.nextInt();

        try {
            // Convert X to decimal
            long decimalValue = convertToDecimal(numberX, baseX);

            // Convert decimal to target base Y
            String numberY = convertFromDecimal(decimalValue, baseY);

            // Output the result
            System.out.println("The number " + numberX + " in base " + baseX + " is " + numberY + " in base " + baseY);
        } catch (IllegalArgumentException e) {
            System.out.println(e.getMessage());
        }

        scanner.close();
    }
}