用Java写一个文件加密与解密的基础程序

好的，以下是一个基础的Java文件加密与解密程序示例：

import java.io.*;
import java.security.*;

import javax.crypto.*;
import javax.crypto.spec.*;

public class FileEncryptorDecryptor {
    private Cipher ecipher;
    private Cipher dcipher;

    // 构造方法，传入密钥
    public FileEncryptorDecryptor(SecretKey key) throws Exception {
        ecipher = Cipher.getInstance("AES");
        dcipher = Cipher.getInstance("AES");
        ecipher.init(Cipher.ENCRYPT_MODE, key);
        dcipher.init(Cipher.DECRYPT_MODE, key);
    }

    // 加密文件方法
    public void encrypt(File inputFile, File outputFile) throws Exception {
        FileInputStream inputStream = new FileInputStream(inputFile);
        FileOutputStream outputStream = new FileOutputStream(outputFile);
        byte[] buffer = new byte[4096];
        int bytesRead;
        while ((bytesRead = inputStream.read(buffer)) != -1) {
            byte[] encryptedBytes = ecipher.update(buffer, 0, bytesRead);
            outputStream.write(encryptedBytes);
        }
        byte[] encryptedBytes = ecipher.doFinal();
        outputStream.write(encryptedBytes);
        inputStream.close();
        outputStream.close();
    }

    // 解密文件方法
    public void decrypt(File inputFile, File outputFile) throws Exception {
        FileInputStream inputStream = new FileInputStream(inputFile);
        FileOutputStream outputStream = new FileOutputStream(outputFile);
        byte[] buffer = new byte[4096];
        int bytesRead;
        while ((bytesRead = inputStream.read(buffer)) != -1) {
            byte[] decryptedBytes = dcipher.update(buffer, 0, bytesRead);
            outputStream.write(decryptedBytes);
        }
        byte[] decryptedBytes = dcipher.doFinal();
        outputStream.write(decryptedBytes);
        inputStream.close();
        outputStream.close();
    }

    public static void main(String[] args) throws Exception {
        // 生成密钥
        KeyGenerator keyGenerator = KeyGenerator.getInstance("AES");
        keyGenerator.init(128);
        SecretKey key = keyGenerator.generateKey();

        // 加密文件
        FileEncryptorDecryptor encryptor = new FileEncryptorDecryptor(key);
        encryptor.encrypt(new File("input.txt"), new File("encrypted.bin"));

        // 解密文件
        FileEncryptorDecryptor decryptor = new FileEncryptorDecryptor(key);
        decryptor.decrypt(new File("encrypted.bin"), new File("decrypted.txt"));
    }
}

这里使用了AES对称加密算法，可以根据需要选择不同的算法。需要注意的是，这里的密钥生成方式是随机生成的，实际应用中需要使用更为安全的密钥生成方式。