java实现文件加解密DES

Java中可以使用javax.crypto包中的DES算法来实现文件的加解密。下面是一个简单的示例代码：

import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;
import java.io.*;

public class FileEncryptor {
    private static final String ALGORITHM = "DES";
    private static final String TRANSFORMATION = "DES/ECB/PKCS5Padding";
    private static final String KEY = "YOUR_KEY"; // 8个字符的密钥

    public static void encrypt(File inputFile, File outputFile) throws Exception {
        doCrypto(Cipher.ENCRYPT_MODE, inputFile, outputFile);
    }

    public static void decrypt(File inputFile, File outputFile) throws Exception {
        doCrypto(Cipher.DECRYPT_MODE, inputFile, outputFile);
    }

    private static void doCrypto(int cipherMode, File inputFile, File outputFile) throws Exception {
        try (FileInputStream inputStream = new FileInputStream(inputFile);
             FileOutputStream outputStream = new FileOutputStream(outputFile)) {

            SecretKeySpec secretKey = new SecretKeySpec(KEY.getBytes(), ALGORITHM);
            Cipher cipher = Cipher.getInstance(TRANSFORMATION);
            cipher.init(cipherMode, secretKey);

            byte[] inputBytes = new byte[(int) inputFile.length()];
            inputStream.read(inputBytes);

            byte[] outputBytes = cipher.doFinal(inputBytes);

            outputStream.write(outputBytes);
        }
    }

    public static void main(String[] args) {
        File inputFile = new File("input.txt");
        File encryptedFile = new File("encrypted.txt");
        File decryptedFile = new File("decrypted.txt");

        try {
            encrypt(inputFile, encryptedFile);
            decrypt(encryptedFile, decryptedFile);
            System.out.println("File encryption and decryption completed.");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

请注意，上述代码中的密钥`KEY`应该是8个字符的字符串。你可以根据需要修改密钥和文件名，并确保文件存在。加密后的文件将保存在`encrypted.txt`，解密后的文件将保存在`decrypted.txt`。

请记得在使用加密算法时，要妥善保管好密钥，以确保数据的安全性。