/*
* 凱撒密碼的實現
*/
import java.io.*;
public class Encryptor {
private int key;
public Encryptor(int aKey) {
key = aKey;
}
public void encryptFile(String inFile, String outFile) throws IOException {
InputStream in = null;
OutputStream out = null;
try {
in = new FileInputStream(inFile);
out = new FileOutputStream(outFile);
encrypStream(in,out);
}
finally {
if(in != null ) in.close();
if(out != null ) out.close();
}
}
public void encrypStream(InputStream in, OutputStream out) throws IOException {
boolean done = false;
while (!done) {
int next = in.read();
if (next == -1) done = true;
else {
byte b = (byte) next;
byte c = encrypt(b);
out.write(c);
}
}
}
public byte encrypt(byte b) {
return (byte) (b + key);
}
}
以下爲運行的主類：
import java.io.*;
import java.util.*;
public class EncryptorTester {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
try {
System.out.print("Input file: ");
String inFile = in.next();
System.out.print("Output file: ");
String outFile = in.next();
System.out.print("Encryption key: ");
int key = in.nextInt();
Encryptor crypt = new Encryptor(key);
crypt.encryptFile(inFile, outFile);
} catch (IOException e) {
System.out.println("Error processing file : " + e);
}
}
}