用java实现对文本文件进行加密和解密操作

可以使用Java的加密解密API来对文本文件进行加密和解密操作。下面是一个简单的示例代码：

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileReader;
import java.io.FileWriter;
import java.security.Key;
import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;

public class FileEncryptionDecryption {
    
    private static final String ALGORITHM = "AES";
    private static final String TRANSFORMATION = "AES/ECB/PKCS5Padding";
    private static final String KEY_FILE = "key.txt";
    
    public static void encrypt(String inputFile, String outputFile) throws Exception {
        Key secretKey = getSecretKey();
        Cipher cipher = Cipher.getInstance(TRANSFORMATION);
        cipher.init(Cipher.ENCRYPT_MODE, secretKey);
        
        try (BufferedReader reader = new BufferedReader(new FileReader(inputFile))) {
            try (BufferedWriter writer = new BufferedWriter(new FileWriter(outputFile))) {
                String line;
                while ((line = reader.readLine()) != null) {
                    byte[] encrypted = cipher.doFinal(line.getBytes());
                    writer.write(Base64.getEncoder().encodeToString(encrypted));
                    writer.newLine();
                }
            }
        }
    }

    public static void decrypt(String inputFile, String outputFile) throws Exception {
        Key secretKey = getSecretKey();
        Cipher cipher = Cipher.getInstance(TRANSFORMATION);
        cipher.init(Cipher.DECRYPT_MODE, secretKey);
        
        try (BufferedReader reader = new BufferedReader(new FileReader(inputFile))) {
            try (BufferedWriter writer = new BufferedWriter(new FileWriter(outputFile))) {
                String line;
                while ((line = reader.readLine()) != null) {
                    byte[] encrypted = Base64.getDecoder().decode(line);
                    byte[] decrypted = cipher.doFinal(encrypted);
                    writer.write(new String(decrypted));
                    writer.newLine();
                }
            }
        }
    }
    
    private static Key getSecretKey() throws Exception {
        Key secretKey;
        if (new File(KEY_FILE).exists()) {
            try (ObjectInputStream ois = new ObjectInputStream(new FileInputStream(KEY_FILE))) {
                secretKey = (Key) ois.readObject();
            }
        } else {
            KeyGenerator keyGenerator = KeyGenerator.getInstance(ALGORITHM);
            keyGenerator.init(128);
            secretKey = keyGenerator.generateKey();
            try (ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(KEY_FILE))) {
                oos.writeObject(secretKey);
            }
        }
        return secretKey;
    }
}

在上面的示例代码中，我们使用了AES算法来进行加密和解密操作。我们还使用了Base64来对加密后的文本进行编码，以便于在文件中进行存储和读取。

你可以通过调用 `encrypt` 方法来加密一个文本文件，调用 `decrypt` 方法来解密一个加密后的文本文件。

下面是一个使用示例：

public static void main(String[] args) throws Exception {
    FileEncryptionDecryption.encrypt("original.txt", "encrypted.txt");
    FileEncryptionDecryption.decrypt("encrypted.txt", "decrypted.txt");
}

在上面的示例中，我们将 `original.txt` 文件加密并保存到 `encrypted.txt` 文件中，然后将加密后的文本文件解密并保存到 `decrypted.txt` 文件中。