在Java中，可以使用javax.crypto包中的Cipher類來實現AES加密算法。以下是一個簡單的示例代碼來演示如何使用AES加密算法對字符串進行加密和解密：

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;
import java.util.Base64;

public class AESEncryption {

    public static SecretKey generateAESKey() throws Exception {
        KeyGenerator keyGenerator = KeyGenerator.getInstance("AES");
        keyGenerator.init(128);
        return keyGenerator.generateKey();
    }

    public static String encrypt(String data, SecretKey key) throws Exception {
        Cipher cipher = Cipher.getInstance("AES");
        cipher.init(Cipher.ENCRYPT_MODE, key);
        byte[] encryptedBytes = cipher.doFinal(data.getBytes());
        return Base64.getEncoder().encodeToString(encryptedBytes);
    }

    public static String decrypt(String encryptedData, SecretKey key) throws Exception {
        Cipher cipher = Cipher.getInstance("AES");
        cipher.init(Cipher.DECRYPT_MODE, key);
        byte[] decryptedBytes = cipher.doFinal(Base64.getDecoder().decode(encryptedData));
        return new String(decryptedBytes);
    }

    public static void main(String[] args) throws Exception {
        SecretKey key = generateAESKey();

        String data = "Hello, AES!";
        String encryptedData = encrypt(data, key);
        System.out.println("Encrypted data: " + encryptedData);

        String decryptedData = decrypt(encryptedData, key);
        System.out.println("Decrypted data: " + decryptedData);
    }
}

在上面的示例中，我們首先使用generateAESKey()方法生成一個AES密鑰，然后使用encrypt()方法對字符串進行加密，最后使用decrypt()方法將加密后的字符串解密。最后，我們在main()方法中演示了整個加密和解密的過程。