题解 | 字符串加解密

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

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String s = scanner.nextLine(); // 明文
        String t = scanner.nextLine(); // 密文

        // 加密映射：明文 → 密文
        Map<Character, Character> encryptMap = new HashMap<>();
        // 字母映射（大写）
        for (char c = 'A'; c <= 'Z'; c++) {
            char encrypted = (char) ('a' + (c - 'A' + 1) % 26);
            encryptMap.put(c, encrypted);
        }
        // 字母映射（小写）
        for (char c = 'a'; c <= 'z'; c++) {
            char encrypted = (char) ('A' + (c - 'a' + 1) % 26);
            encryptMap.put(c, encrypted);
        }
        // 数字映射
        for (char c = '0'; c <= '9'; c++) {
            char encrypted = (char) ('0' + (c - '0' + 1) % 10);
            encryptMap.put(c, encrypted);
        }

        // 解密映射：密文 → 明文
        Map<Character, Character> decryptMap = new HashMap<>();
        // 字母映射（小写密文→大写明文）
        for (char c = 'a'; c <= 'z'; c++) {
            char decrypted = (char) ('A' + (c - 'a' - 1 + 26) % 26);
            decryptMap.put(c, decrypted);
        }
        // 字母映射（大写密文→小写明文）
        for (char c = 'A'; c <= 'Z'; c++) {
            char decrypted = (char) ('a' + (c - 'A' - 1 + 26) % 26);
            decryptMap.put(c, decrypted);
        }
        // 数字映射
        for (char c = '0'; c <= '9'; c++) {
            char decrypted = (char) ('0' + (c - '0' - 1 + 10) % 10);
            decryptMap.put(c, decrypted);
        }

        // 加密明文s
        StringBuilder encrypted = new StringBuilder();
        for (char c : s.toCharArray()) {
            encrypted.append(encryptMap.get(c));
        }

        // 解密密文t
        StringBuilder decrypted = new StringBuilder();
        for (char c : t.toCharArray()) {
            decrypted.append(decryptMap.get(c));
        }

        // 输出结果
        System.out.println(encrypted.toString());
        System.out.println(decrypted.toString());

        scanner.close();
    }
}

解题思路就是用map把该有的大小写字母都用键值对应好，然后输入的字符串挨个取出对应的值就好了