The Advanced Encryption Standard

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

public class AES {
        static Cipher my_cipher;

        public static void main(String[] args) throws Exception {
            // Build the key  on the server.
                KeyGenerator keyGenerator = KeyGenerator.getInstance("AES");
                keyGenerator.init(128);
                SecretKey my_secretKey = keyGenerator.generateKey();
            // Prepare a version of the key to send to the client
                String encodedKey = Base64.getEncoder().encodeToString(my_secretKey.getEncoded());
                System.out.println("\nThe Key: "+encodedKey+"\n");
                System.out.println("The key length is: "+ encodedKey.length()+"\n");
            // Rebuild the key using SecretKeySpec on the client.
                byte[] decodedKey = Base64.getDecoder().decode(encodedKey);
               SecretKey originalKey = new SecretKeySpec(decodedKey, 0, decodedKey.length, "AES"); 
                my_cipher = Cipher.getInstance("AES");
            // On the Server
                String plainText = "A Simple Demonstration of AES";
                System.out.println("Plain Text Before Encryption: " + plainText+"\n");
                String encryptedText = encrypt(plainText, my_secretKey);
                System.out.println("Encrypted Text After Encryption: " + encryptedText+"\n");
            // On the Client
                String decryptedText = decrypt(encryptedText, originalKey);
                System.out.println("Decrypted Text After Decryption: " + decryptedText+"\n");
        }

        public static String encrypt(String plainText, SecretKey a_secretKey)
                        throws Exception {
                byte[] plainTextByte = plainText.getBytes();
                my_cipher.init(Cipher.ENCRYPT_MODE, a_secretKey);
                byte[] encryptedByte = my_cipher.doFinal(plainTextByte);
                Base64.Encoder encoder = Base64.getEncoder();
                String encryptedText = encoder.encodeToString(encryptedByte);
                return encryptedText;
        }

        public static String decrypt(String encryptedText, SecretKey a_secretKey)
                        throws Exception {
                Base64.Decoder decoder = Base64.getDecoder();
                byte[] encryptedTextByte = decoder.decode(encryptedText);
                my_cipher.init(Cipher.DECRYPT_MODE, a_secretKey);
                byte[] decryptedByte = my_cipher.doFinal(encryptedTextByte);
                String decryptedText = new String(decryptedByte);
                return decryptedText;
        }
}