java - Convert a letter to the corresponding letter on the opposite counting direction in the alphabet -

i self-studying java , @ beginning learning basics. below code trying convert letter corresponding letter on opposite counting direction in alphabet(i.e z or z etc.). works single letter not series of letters. how can make work more 1 letter? if can use simplest way quite new in java. don't(know how to) export built in classes etc.

thank you.

class turner{     int find(int fin, int mi,int ma,char ch[]){         int mid = (ma+mi)/2;         int x;         if(ch[mid]==fin)             return mid;         else if(fin<ch[mid])             return(find(fin, mi,mid-1,ch));         else              return x = find(fin,(mid+1),ma,ch);     }  }  class turn {     public static void main(string args[]) throws java.io.ioexception     {         turner try1 = new turner();            char arra[] = new char[26];         char arrb[] = new char[26];         int min = 0;         int max = arra.length;         char = 'a';         char b = 'z';         int i;         char letter;         for(i=0;i<26;i++)         {             arra[i]=a;             a++;             arrb[i]=b;             b--;         }          system.out.println("enter letter: ");          letter = (char)system.in.read();         system.out.print(arrb[try1.find(letter,min,max,arra)]);     } } 

have considered doing math?

letter = character.touppercase((char)system.in.read()); system.out.print((char)('z' - (letter - 'a')); 

and works 1 letter because not repeating conversion procedure. program reads 1 char, prints opposite , terminates.

all have put read , print code inside sort of loop, every time runs promptly wait next letter.

while (true) {     letter = character.touppercase((char)system.in.read());     if ((letter > 'z') || (letter < 'a'))         break;  // user inputted invalid symbol, terminating program     system.out.print((char)('z' - (letter - 'a'))); }