java 实现3DES加密解密

Java中实现3DES加密解密可以使用JCE（Java Cryptography Extension）提供的API。下面是一个简单的示例代码：

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.DESedeKeySpec;
import java.nio.charset.StandardCharsets;
import java.security.spec.KeySpec;

public class TripleDesExample {
    public static void main(String[] args) throws Exception {
        String plainText = "Hello, world!";
        String secretKey = "0123456789ABCDEFGHIGKLMN";
        
        byte[] encryptedBytes = encrypt(plainText, secretKey);
        String encryptedText = new String(encryptedBytes, StandardCharsets.UTF_8);
        System.out.println("Encrypted text: " + encryptedText);
        
        byte[] decryptedBytes = decrypt(encryptedBytes, secretKey);
        String decryptedText = new String(decryptedBytes, StandardCharsets.UTF_8);
        System.out.println("Decrypted text: " + decryptedText);
    }

    public static byte[] encrypt(String plainText, String secretKey) throws Exception {
        byte[] plainBytes = plainText.getBytes(StandardCharsets.UTF_8);
        byte[] keyBytes = secretKey.getBytes(StandardCharsets.UTF_8);
        KeySpec keySpec = new DESedeKeySpec(keyBytes);
        SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("DESede");
        SecretKey key = keyFactory.generateSecret(keySpec);
        Cipher cipher = Cipher.getInstance("DESede");
        cipher.init(Cipher.ENCRYPT_MODE, key);
        return cipher.doFinal(plainBytes);
    }

    public static byte[] decrypt(byte[] encryptedBytes, String secretKey) throws Exception {
        byte[] keyBytes = secretKey.getBytes(StandardCharsets.UTF_8);
        KeySpec keySpec = new DESedeKeySpec(keyBytes);
        SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("DESede");
        SecretKey key = keyFactory.generateSecret(keySpec);
        Cipher cipher = Cipher.getInstance("DESede");
        cipher.init(Cipher.DECRYPT_MODE, key);
        return cipher.doFinal(encryptedBytes);
    }
}

在上面的示例代码中，我们使用了`DESede`算法实现了3DES加密解密。需要注意的是，密钥的长度必须是24个字节（即192位），因此我们在示例中使用了一个24个字符的字符串作为密钥。在实际应用中，我们可以使用更加安全的方式生成密钥，例如使用`KeyGenerator`类生成密钥。