Steps for Deciphering the message

1. remove 3 at end of the string
2. replace ASCII values at even places(number clusters) with corresponding characters value.
3. replace * with spacing " ".
4. reverse the string
5. swap case of string- lowercase to upper case and vice versa.

Sample input: ?85O89*69R65*87O104*33I1043 Require output: Hi! How are you? This is the whole method that I have written.

public String deciphering(String ciphered) {
        StringBuilder a = new StringBuilder(ciphered);
        StringBuilder b = a.deleteCharAt(a.length()-1);
        char[] ch = new char[b.length()];
        StringBuilder c = new StringBuilder();
        for (int i = 0; i < b.length(); i  ) {
            ch[i] = b.charAt(i);
        }
        for (int i = 0; i < ch.length; i  ) {
            if(!Character.isDigit(ch[i]))
            {
                c.append(ch[i]);
            }else
            {
                String temp = new String();
                while(Character.isDigit(ch[i]) &&(i<b.length())){
                   temp = temp   ch[i];
                   i  ;
               }
                int number = Integer.parseInt(temp);
                char p = (char)number;
               c.append(p);
            }
        }

        String d = c.toString();
        String e = d.replace('*', ' ');
        StringBuffer f = new StringBuffer(e);
        StringBuffer g = f.reverse();
        for (int i = 0; i < g.length(); i  ) {

                if (Character.isLowerCase(g.charAt(i))){
                    char x = Character.toUpperCase(g.charAt(i));
                    g.setCharAt(i, x);
                } else if (Character.isUpperCase(g.charAt(i))) {
                    char x = Character.toLowerCase(g.charAt(i));
                    g.setCharAt(i, x);
                }
        }

        return g.toString();
    }

CodePudding user response：

It may be better to split the input string into parts with non-digit delimiters and keep the delimiters using the following regular expression (using look-ahead and look-behind as described here) after removing the last character:

str.substring(0, str.length() - 1).split("(?<=\\D)|(?=\\D)")

Then Stream API may be used to convert each string into a separate character and insert these characters into prepared StringBuilder to implement reverse order in the result:

public static String decipher(String str) {
    
    StringBuilder sb = new StringBuilder(str.length());
    
    Arrays.stream(
            str.substring(0, str.length() - 1).split("(?<=\\D)|(?=\\D)")
        )
        .map(p -> p.matches("\\d ") ? (char) Integer.parseInt(p): p.charAt(0))
        .map(c -> c == '*' ? ' ' 
            : Character.isLowerCase(c) ? Character.toUpperCase(c) 
            : Character.isUpperCase(c) ? Character.toLowerCase(c)
            : c
        )
        .forEach(c -> sb.insert(0, c));
        
    return sb.toString();
}

Test:

System.out.println(decipher("?85O89*69R65*87O104*33I1043"));

Output:

Hi! How are you?

CodePudding user response：

You are incrementing i twice past the last digit of a chunk - when you exit your inner loop i is indexing the first non-digit character, then when you reach the end of the for loop body, the for loop is incrementing i again.