Thread: CaesarCipher

Im trying to encrypt a .txt file using the CaesarCipher method.
Below is what i have so far after roughly following an example in Horstmann's book.

I get errors when trying to compile "reader" and im pretty sure there is an error when trying to initialize encrypt scanner. Any help would be great.

PHP Code:

import java.util.Scanner;
import java.io.*;

public class CaesarCipher
{
    public CaesarCipher(int aKey)
    {
        Key = 4;
    }
    public void encryptScanner(Scanner in, PrintWriter out)
    throws exception IOException
    {
        boolean done = false;
        while (!done)
        {
            int next = in.read();
            if (next == -1) done = true;
            else
            {
                char c = (char) next;
                char b = encrypt(c);
                out.write(c);
            }
        }
    }
    public char encrypt(char c)
    {
        return (char) (c + Key);
    }
    private int Key;
} 


PHP Code:

import java.io.FileReader;
import java.util.Scanner;
import java.io.*;

public class reader
{
    public static void main( String[] args)
    throws IOException
    {
        File file = new File("poem.txt");
        Scanner in = new Scanner(file);
        PrintWriter out = new PrintWriter("encrypted.txt");
        
        CaesarCipher cipher = new CaesarCipher(Key);
        cipher.encryptScanner(Scanner, PrintWriter);
        
    
        in.close();
        out.close();
    }
} 


I believe this line to be the culprit in reader.java:

PrintWriter out = new PrintWriter("encrypted.txt");

If that's of no help take a look at: PrintWriter (Java 2 Platform SE v1.4.2) will tell you everything you wanted to know about PrintWriters and more. Compare how you've used the printwriter to the notes about how to use it in that way on that page. Maybe I'm wrong on this one, but I'm pretty sure that's at least not a preferred way to do things.

Also think about the arguments you've passed to the encryptScanner() method, they aren't variables, what are they?

The key from the example im following originally came from a keyboard input but im trying to define it in the first piece of code. As for the Print writer, would i be better using FileWriter?

I get errors when trying to compile "reader"

Please copy and paste here the full text of the error messages.

reader.java:14: cannot find symbol
symbol : class CaesarCipher
location: class reader
CaesarCipher cipher = new CaesarCipher();
^
reader.java:14: cannot find symbol
symbol : class CaesarCipher
location: class reader
CaesarCipher cipher = new CaesarCipher();
^
reader.java:15: cannot find symbol
symbol : variable Scanner
location: class reader
cipher.encryptScanner(Scanner, FileWriter);
^
reader.java:15: cannot find symbol
symbol : variable FileWriter
location: class reader
cipher.encryptScanner(Scanner, FileWriter);
^
4 errors

Those are the 4 errors i get, but im still not convinced that the code is right for cipher.encryptScanner(Scanner, FileWriter) and the relating section in CaesarCipher.

Thanks for the replies so far.

Does this error message go with the code you posted for the reader class?
Error message source reference: CaesarCipher cipher = new CaesarCipher();
reader class source: CaesarCipher cipher = new CaesarCipher(Key);

The code you posted is different from the code in the error message.
Can you explain?

Oh sorry Norm!
I just took out (Key) to see if it made a difference but hadnt put it back in. It adds another error in as you can see below.

symbol : class CaesarCipher
location: class reader
CaesarCipher cipher = new CaesarCipher(Key);
^
reader.java:14: cannot find symbol
symbol : class CaesarCipher
location: class reader
CaesarCipher cipher = new CaesarCipher(Key);
^
reader.java:14: cannot find symbol
symbol : variable Key
location: class reader
CaesarCipher cipher = new CaesarCipher(Key);
^
reader.java:15: cannot find symbol
symbol : variable Scanner
location: class reader
cipher.encryptScanner(Scanner, FileWriter);
^
reader.java:15: cannot find symbol
symbol : variable FileWriter
location: class reader
cipher.encryptScanner(Scanner, FileWriter);
^
5 errors

Did the CaesarCipher class compile OK? Where is its .class file?

cipher.encryptScanner(Scanner, FileWriter);

You need to use variable names here, not the names of the classes.

cannot find symbol
symbol : variable Key

Where is the variable Key defined?

So the variables would be file and out then? or in and out?

CaesarCipher.java:17: cannot find symbol
symbol : method read()
location: class java.util.Scanner
int next = in.read();
^
1 error

It did compile but not now for some reason, i had one error with throws exception IOException so changed it to throws IOException. After i fixed that the above error came about.

Originally Posted by Norm

Where is the variable Key defined?

PHP Code:

public class CaesarCipher
{
    public CaesarCipher(int aKey)
    {
        Key = 4; 


On the original example this was defined by the user inputting a value of their choice. I decided to just try and define it with no user input needed.

Key = 4;

That does not define the varible Key. It gives the variable Key a value of 4.
You need a data type before a variable name to define a variable:
<datatype> var_name = ...
where <datatype> is the data type of the variable. For example: int, double, CaesarCipher (your class is a data type)

cannot find symbol
symbol : method read()

What class is the method read() defined in?
Is the variable in an instance of that class?

Read the API doc for the class: Java Platform SE 6