Caesar Cipher Algorithm Wrong ??

Question

public class caesarCipher {
      public static void main(String args[]) {
      int num1=0,donothing=0;
      char[] s1 = {'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o',
      'p','q','r','s','t','u','v','w','x','y','z'};
      System.out.println("Please enter a caesar cipher shift between 1-26 :");
      num1 = SavitchIn.readInt();
          do {
                System.out.println("ERROR: Please enter a caesar cipher shift between 1-26 :");
                num1 = SavitchIn.readInt();
          }while(num1>26 && num1<1);
          while(num1<27 && num1>0) {
                System.out.println("Please enter some plaintext to be  encoded");
                String s2 = SavitchIn.readLine();
                s2=s2.toLowerCase();
                int length1 = s2.length();
                for (int i=0; i<s2.length(); i++) {
                      for (int j=0; j<s2.length(); j++) {
                            if( s2.charAt(i)==s1[j] )
                                  System.out.print( s1[(j+num1)%26] );
                            else if ( s2.charAt(i)!=s1[j] )
                                  donothing++;
                System.out.println();
                System.exit(0);
}The program works fine if the user enters abc.. but if anything else is entered e.g fghkl the program prints a blank.
Any ideas where I went wrong on this as I am pulling my hair out trying to work it out :)
Thanks for any help
Se�n

Answer 1

I tried 26 instead of s1.length(), thanks for the help
as the idea was correct.No, no, no. Again, use s1.length (not s1.length()). Don't hard-code constants like "26", as then your code is more fragile if you change the actual array size.