cypher.java

class cypher {
    public static void main(String[] args) {
            if(args.length!=4){
            System.err.println("Incorrect usage. -[e,d] even odd message");
            System.err.println("If your message has spaces, you need to use quotes.");
            System.exit(0);
        }
        int a=0;
        int b=0;
        if(args[0].equals("-e"))
        {a = Integer.parseInt(args[1]);
            b = Integer.parseInt(args[2]);}
        else if (args[0].equals("-d")) {
            a = -Integer.parseInt(args[1]);
            b = -Integer.parseInt(args[2]);
        }
        else {
            System.err.println("Incorrect usage. -[e,d] even odd message");
            System.exit(0);
        }
        String t = args[3];
        char[] ct = t.toCharArray();
        boolean even = true;
        int diff =0;
        System.out.println(ct);
        for(int l=0;l<t.length();l++){
            if(ct[l]!=' '){
                if(even){
                    ct[l] = (char)(a + (int)ct[l]);
                }
                else {
                    ct[l] = (char)(b + (int)ct[l]);
                }
                
                if((int)ct[l]>(int)'z')
                {
                    diff = (int)ct[l] - ((int)'z'+1);
                    ct[l] = (char)(diff+(int)'a');}
                if((int)ct[l]<(int)'a')
                {
                    diff = (int)ct[l] - ((int)'a'-1);
                    ct[l] = (char)(diff+(int)'z');}
            }
            even=!even;
        }
        System.out.println(ct);
        
    }
}