在使用AES加密算法时，需要确定填充方案，以确保数据块的长度为128位。以下是一个示例，使用Java中的Crypto库实现AES加密算法并指定填充方案为PKCS5Padding：

import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;

public class AES {

    private static final byte[] key = "secretkey123456".getBytes(); // 16 byte key

    public static byte[] encrypt(String plainText) throws Exception {
        SecretKeySpec secretKey = new SecretKeySpec(key, "AES");
        Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
        cipher.init(Cipher.ENCRYPT_MODE, secretKey);
        return cipher.doFinal(plainText.getBytes());
    }

    public static String decrypt(byte[] cipherText) throws Exception{
        SecretKeySpec secretKey = new SecretKeySpec(key, "AES");
        Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
        cipher.init(Cipher.DECRYPT_MODE, secretKey);
        return new String(cipher.doFinal(cipherText));
    }

    public static void main(String args[]) throws Exception {
        String plainText = "Hello, world!";
        byte[] cipherText = encrypt(plainText);
        String decryptedText = decrypt(cipherText);

        System.out.println("Plain text: " + plainText);
        System.out.println("Encrypted text: " + new String(cipherText));
        System.out.println("Decrypted text: " + decryptedText);
    }
}

在此示例中，我们指定了填充方案为PKCS5Padding。如果要使用其他填充方案，请使用相应的字符串替换“PKCS5Padding”。