Encoding String using an encoding code

Question

Following is my code snippet:

 for (int i=0;i<(in.length());i++)
    {
        char e=cop.charAt(i);
        if (e==' ')
        {
            sav=sav+" ";
            continue;
        }
        int n=(int)e;
        if (n>=(91-ef))
        {
            //here is where the statement should be
            continue;
        }    
        n=n+ef;
        sav=sav+((char)n);
    }

in: String entered by the user

ef: encoding factor entered by the user

sav: in which I'm storing my modified String

Here what I need to do is input a string (word or sentence) in upper case and increase the ASCII value of each character of the string by an encoding factor entered by the user and print the respective character at the new ASCII value. Spaces will remain spaces and if the character should exceed 'Z', it'll start again from 'A'. It's the last part I'm having problem with. There should be one statement at the place I've commented in the above code but I can't figure out what it should be. Please help?

Here's an example what I need to do:

INPUT: tommy

OUTPUT: YTRRD (when the encoding factor is 5)

I know, I've converted it to upper case earlier in the code. — Shinjinee Maiti
– Shinjinee Maiti, Commented May 16, 2016 at 12:58

Peter Lawrey · Accepted Answer · 2016-05-18 08:37:16Z

1

I would add first and then check it using using characters instead of raw numbers.

e = Character.toUpperCase(e);
e += 5;
if (e > 'Z')
   e -= 'Z' + 1 - 'A';
sav += e;

or using a constant.

static final int LETTERS_IN_ALPHABET = 'Z' + 1 - 'A';

// in code
e = Character.toUpperCase(e);
e += 5;
if (e > 'Z')
   e -= LETTERS_IN_ALPHABET;
sav += e;

edited May 18, 2016 at 8:37

answered May 16, 2016 at 12:57

Peter Lawrey

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6 Comments

Shinjinee Maiti Over a year ago

Please explain the 4th line?

Arnaud Denoyelle Over a year ago

@ShinjineeMaiti Suppose that e = 'Z' and ef = 1. This line takes the value of e back to 'A' instead of 'Z'+1.

Peter Lawrey Over a year ago

It subtracts 26 without having to calculate how many letters there are. 'Z' + 1 becomes 'A', 'Z' + 2 becomes 'B' etc.

Tom Blodget Over a year ago

To resolve any question, put the result of the expression…in a constant with a name that explains the purpose.

Peter Lawrey Over a year ago

@TomBlodget Equations are not as readable to some people. English would be better.

|

dryairship · Accepted Answer · 2016-05-16 13:11:48Z

0

In your code, this should work:

if (n>=(91-ef))
{
     n = 64 + (n+ef-90) -ef;
}

There is no need for continue.
n+ef is the final "normal" value, eg: Y=89, so, on adding 5, it becomes 94.
-90 to check by how much it is greater than 90, i.e, 4 (in case of Y).
64 + (n+ef-90) - Then add that number to 64, i.e. 64+4 = 68 = D
-ef as you add ef after that. The line after this piece of code is : n=n+ef;. That would make 68+4 = 72 = H. But you already have the needed char, i.e., D, so you subtract ef so it becomes 68-5 = 63. Then, in the next line, you add it to get 63+5 = 68 = D.

edited May 16, 2016 at 13:11

answered May 16, 2016 at 13:04

dryairship

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6 Comments

Shinjinee Maiti Over a year ago

Didn't get the last bullet. Please re-explain?

dryairship Over a year ago

@ShinjineeMaiti Did you get it now?

Shinjinee Maiti Over a year ago

Now I get what you mean, but if you notice I've given a 'continue' after that so no need for the last bullet. Thanks though.

dryairship Over a year ago

@ShinjineeMaiti You should not use continue. If you do, then the line sav=sav+((char)n); will not be executed, and the char will not be added to sav

Shinjinee Maiti Over a year ago

I would directly convert that ASCII value to char in the same line itself

|

Arnaud Denoyelle · Accepted Answer · 2016-05-16 13:21:52Z

0

Follow these steps :

e is a character in ASCII code. Convert it to a [0-25] value using e - 'A'
Then add ef
As the result can exceed 25 (i.e e > 'Z'), use a modulo 26
Finally, add 'A' to the result in order to convert the value back to a ['A'-'Z'] value.

Code :

String in = "TOMMY";
String sav="";
int ef = 5;

for (int i=0;i<(in.length()); i++) {
  char e=in.charAt(i);
  if (e==' ')
  {
    sav=sav+" ";
  } else {
    sav += (char) ('A' + ((e - 'A' + ef) % 26));
  }
}

System.out.println(sav);

result :

YTRRD

Note : Using String+= is bad. use a StringBuilder instead.
Note : Replace (e - 'A' + ef) with (e - 'A' + ef + 26) if you want to enable negative values for ef.

edited May 16, 2016 at 13:21

answered May 16, 2016 at 13:08

Arnaud Denoyelle

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