Java提供了對稱加密和不對稱加密兩種加密方式。

對稱加密是指加密和解密使用相同密鑰的加密方式。Java中常用的對稱加密算法有DES、AES、RC4等。以下是使用AES算法進行對稱加密的示例代碼：

import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;
import java.util.Base64;
public class AESEncryptor {
private static final String KEY = "abcdefghijklmnop";
public static String encrypt(String data) throws Exception {
SecretKeySpec secretKeySpec = new SecretKeySpec(KEY.getBytes(), "AES");
Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec);
byte[] encryptedBytes = cipher.doFinal(data.getBytes("UTF-8"));
return Base64.getEncoder().encodeToString(encryptedBytes);
}
}

不對稱加密是指加密和解密使用不同密鑰的加密方式。Java中常用的不對稱加密算法有RSA、DSA等。以下是使用RSA算法進行不對稱加密的示例代碼：

import javax.crypto.Cipher;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
public class RSAEncryptor {
private static final String ALGORITHM = "RSA";
public static KeyPair generateKeyPair(int keySize) throws Exception {
KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance(ALGORITHM);
keyPairGenerator.initialize(keySize);
return keyPairGenerator.generateKeyPair();
}
public static byte[] encrypt(byte[] data, PublicKey publicKey) throws Exception {
Cipher cipher = Cipher.getInstance(ALGORITHM);
cipher.init(Cipher.ENCRYPT_MODE, publicKey);
return cipher.doFinal(data);
}
public static byte[] decrypt(byte[] data, PrivateKey privateKey) throws Exception {
Cipher cipher = Cipher.getInstance(ALGORITHM);
cipher.init(Cipher.DECRYPT_MODE, privateKey);
return cipher.doFinal(data);
}
}