import java.util.Scanner;

public class work1 {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
    Scanner scanner=new Scanner(System.in);
    int num=0;
    System.out.println("（1加密字符串，2解密字符串）");
    System.out.print("请选择：");
    num=scanner.nextInt();
 
  if(num==1)
  { 
      System.out.print("请输入需要加密的字符串：");
       String str=scanner.next();
    scanner.close();//这是啥意思？
 System.out.print("加密后：");

    char a=‘a‘; 
   for(int i=0;i<str.length();i++)
   { 
       char a2=str.charAt(i);
   if(a2>=‘A‘&&a2<=‘Z‘)
   {
       if(a2>=‘X‘&&a2<=‘Z‘)
       {
         if(a2==‘X‘) a=‘A‘;
         if(a2==‘Y‘) a=‘B‘;
         if(a2==‘Z‘) a=‘C‘;
       }
       else
       { a=(char)(a2+3);}
    }
    System.out.print(a);}
   }
  if(num==2)
  { 
      System.out.print("请输入需要解密的字符串：");
      String str=scanner.next();
      char b=‘b‘;
  System.out.print("解密后：");
      for(int j=0;j<str.length();j++)
      {char b2=str.charAt(j);
      if(b2>=‘A‘&&b2<‘Z‘)
       {
           if(b2>=‘A‘&&b2<‘D‘)
           {
            if(b2==‘A‘)b=‘X‘;
            if(b2==‘B‘)b=‘Y‘;
            if(b2==‘C‘)b=‘Z‘;
           }
           else
           { b=(char)(b2-3);}
        }
        System.out.print(b);}
       }
    }
}