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import java.io.File; |
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import java.io.IOException; |
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|
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/** |
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A program to run the Caesar cipher encryptor with |
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command line arguments. |
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*/ |
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public class Crypt |
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{ |
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public static void main(String[] args) |
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{ |
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boolean decrypt = false; |
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int key = DEFAULT_KEY; |
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File inFile = null; |
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File outFile = null; |
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|
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if (args.length < 2 || args.length > 4) usage(); |
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|
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try |
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{ |
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for (int i = 0; i < args.length; i++) |
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{ |
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if (args[i].charAt(0) == '-';) |
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{ |
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// it is a command line option |
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char option = args[i].charAt(1); |
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if (option == 'd') |
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decrypt = true; |
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else if (option == 'k') |
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key = Integer.parseInt(args[i].substring(2)); |
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} |
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else |
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{ |
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// it is a file name |
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if (inFile == null) |
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inFile = new File(args[i]); |
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else if (outFile == null) |
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outFile = new File(args[i]); |
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else usage(); |
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} |
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} |
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if (decrypt) key = -key; |
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Encryptor crypt = new Encryptor(key); |
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crypt.encryptFile(inFile, outFile); |
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} |
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catch (NumberFormatException exception) |
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{ |
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System.out.println("Key must be an integer: " + exception); |
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} |
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catch (IOException exception) |
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{ |
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System.out.println("Error processing file: " + exception); |
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} |
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} |
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|
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/** |
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Prints a message describing proper usage and exits. |
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*/ |
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public static void usage() |
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{ |
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System.out.println |
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("Usage: java Crypt [-d] [-kn] infile outfile"); |
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System.exit(1); |
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} |
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|
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public static final int DEFAULT_KEY = 3; |
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} |