java-HJ29_字符串加解密

java-HJ29 字符串加解密

import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    /**
     * mod
     * @param args
     */
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        String needToEncrypt = in.next();
        String needToDecrypt = in.next();
        System.out.println(encrypt(needToEncrypt));
        System.out.println(decrypt(needToDecrypt));
    }

    public static String encrypt(String s) {
        char[] cs = s.toCharArray();
        //foreach拿到的不是元素本身，而是一个新变量，所以这里不能用foreach
        //除非新建一个StringBuilder
        for(int i=0;i<s.length();i++) {
            if(cs[i]>='a' && cs[i]<='z') {
                cs[i] = (char) ((cs[i]-'a'+1)%26 + 'A');
            }else if(cs[i]>='A' && cs[i]<='Z') {
                cs[i] = (char) ((cs[i]-'A'+1)%26 + 'a');
            }else if(cs[i]>='0' && cs[i]<='9') {
                cs[i] = (char) ((cs[i]-'0'+1)%10 + '0');
                //0-9是10个数，不是9个！
            }
        }
        return String.valueOf(cs);
    }

    public static String decrypt(String s) {
        char[] cs = s.toCharArray();
        //foreach拿到的不是元素本身，而是一个新变量，所以这里不能用foreach
        //除非新建一个StringBuilder
        //注意减法要再加一个26或10，才可以正常循环起来
        for(int i=0;i<s.length();i++) {
            if(cs[i]>='a' && cs[i]<='z') {
                cs[i] = (char) ((cs[i]-'a'-1+26)%26 + 'A');
            }else if(cs[i]>='A' && cs[i]<='Z') {
                cs[i] = (char) ((cs[i]-'A'-1+26)%26 + 'a');
            }else if(cs[i]>='0' && cs[i]<='9') {
                cs[i] = (char) ((cs[i]-'0'-1+10)%10 + '0');
            }
        }
        return String.valueOf(cs);
    }



//    /**
//     * Character
//     * @param args
//     */
//    public static void main(String[] args) {
//        Scanner in = new Scanner(System.in);
//
//        while (in.hasNext()){
//            String originStr = in.nextLine();
//            String encryptStr = in.nextLine();
//
//            char[] originChars = originStr.toCharArray();
//            char[] encryptChars = encryptStr.toCharArray();
//
//            StringBuilder enc = new StringBuilder();
//            for(char aChar: originChars){
//                if(Character.isLetter(aChar)){
//                    if(Character.isLowerCase(aChar)){
//                        if(aChar=='z'){
//                            enc.append(Character.toUpperCase((char) (aChar-25)));
//                        }else{
//                            enc.append(Character.toUpperCase((char ) (aChar+1)));
//                        }
//                    }
//                    if(Character.isUpperCase(aChar)){
//                        if(aChar=='Z'){
//                            enc.append(Character.toLowerCase((char) (aChar-25)));
//                        }else{
//                            enc.append(Character.toLowerCase((char ) (aChar+1)));
//                        }
//                    }
//                }else if(Character.isDigit(aChar)){
//                    if(aChar=='9'){
//                        enc.append('0');
//                    }else{
//                        enc.append((char ) ((int) aChar +1));
//                    }
//                }else{
//                    enc.append(aChar);
//                }
//
//            }
//            System.out.println(enc);
//
//            StringBuilder dec = new StringBuilder();
//            for(char aChar: encryptChars){
//                if(Character.isLetter(aChar)){
//                    if(Character.isLowerCase(aChar)){
//                        if(aChar=='a'){
//                            dec.append(Character.toUpperCase((char) (aChar+25)));
//                        }else{
//                            dec.append(Character.toUpperCase((char ) (aChar-1)));
//                        }
//                    }
//                    if(Character.isUpperCase(aChar)){
//                        if(aChar=='A'){
//                            dec.append(Character.toLowerCase((char) (aChar+25)));
//                        }else{
//                            dec.append(Character.toLowerCase((char ) (aChar-1)));
//                        }
//                    }
//                }else if(Character.isDigit(aChar)){
//                    if(aChar=='0'){
//                        dec.append('9');
//                    }else{
//                        dec.append((char ) ((int) aChar -1));
//                    }
//                }else{
//                    dec.append(aChar);
//                }
//            }
//            System.out.println(dec);
//        }
//    }
}