init

ciphers/Cipher.java

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+import java.util.*;
+import java.io.*;
+
+// Represents a classical cipher that is able to encode a plaintext into a ciphertext, and
+// decode a ciphertext into a plaintext. Also capable of encoding and decoding entire files
+
+public abstract class Cipher {
+    // The minimum character able to be encoded by any cipher
+    public static final int MIN_CHAR = (int)(' ');
+    
+    // The maximum character able to be encoded by any cipher
+    public static final int MAX_CHAR = (int)('}');
+    
+    // The total number of characters able to be encoded by any cipher (aka. the encodable range)
+    public static final int TOTAL_CHARS = MAX_CHAR - MIN_CHAR + 1;
+
+    // Pre: Throws a FileNotFoundException if a file with the provided 'fileName' doesn't exist
+    // Post: Applies this Cipher's encryption scheme to the file with the given 'fileName', creating
+    //       a new file to store the results.
+    public void encryptFile(String fileName) throws FileNotFoundException {
+        fileHelper(fileName, true, "-encoded");
+    }
+    
+    // Pre: Throws a FileNotFoundException if a file with the provided 'fileName' doesn't exist
+    // Post: Applies this Cipher's decryption scheme (reversing a single round of encryption if applied)
+    //       to the file with the given 'fileName', creating a new file to store the results.
+    public void decryptFile(String fileName) throws FileNotFoundException {
+        fileHelper(fileName, false, "-decoded");
+    }
+    
+    // Pre: Throws a FileNotFoundException if a file with the provided 'fileName' doesn't exist
+    // Post: Reads from an input file with 'fileName', either encrypting or decrypting depending on 'encode',
+    //       printing the results to a new file with 'suffix' appended to the input file's name
+    private void fileHelper(String fileName, boolean encode, String suffix) throws FileNotFoundException{
+        Scanner sc = new Scanner(new File(fileName));
+        String out = fileName.split("\\.txt")[0] + suffix + ".txt";
+        PrintStream ps = new PrintStream(out);
+        while(sc.hasNextLine()) {
+            String line = sc.nextLine();
+            ps.println(encode ? encrypt(line) : decrypt(line));
+        }
+    }
+
+    // Post: Returns the result of applying this Cipher's encryption scheme to 'input'
+    public abstract String encrypt(String input);
+    
+    // Post: Returns the result of applying this Cipher's decryption scheme to 'input'
+    public abstract String decrypt(String input);
+}