Basic example of encode and decode a string using AES:

Code:

package foo;

import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;

import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.spec.SecretKeySpec;

public class EncryptDecryptTest {

 public static Cipher getCipher(
           String synchro1, String synchro2, String synchro3, String synchro4,boolean isEncryptMode)
 throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException
 {
  byte raw[] = (synchro1 + synchro2 + synchro3 + synchro4).getBytes();
  SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
  Cipher cipher = Cipher.getInstance("AES");
  if(isEncryptMode){
   cipher.init(Cipher.ENCRYPT_MODE,skeySpec);
  }
  else{
   cipher.init(Cipher.DECRYPT_MODE,skeySpec);
  } 
  return cipher;
 } 

 public static byte[] hexToByte(String hex)
 {
  byte bts[] = new byte[hex.length() / 2];
  for(int i = 0; i < bts.length; i++){
   bts[i] = (byte)Integer.parseInt(hex.substring(2 * i, 2 * i + 2), 16);
  }

  return bts;
 }

 public static String toHexString(byte bytes[])
 {
  StringBuffer retString = new StringBuffer();
  for(int i = 0; i < bytes.length; i++)
   retString.append(Integer.toHexString(256 + (bytes[i] & 0xff)).substring(1));

  return retString.toString();
 }

 public static String encrypt(String text)
              throws InvalidKeyException, NoSuchAlgorithmException, NoSuchPaddingException, IllegalBlockSizeException, BadPaddingException{
  javax.crypto.Cipher cipher = getCipher("bb5","1860", "17a74", "213f",true);
  return toHexString(cipher.doFinal(text.getBytes()));
 }

 public static String decrypt(String text)
              throws IllegalBlockSizeException, BadPaddingException, InvalidKeyException, NoSuchAlgorithmException, NoSuchPaddingException{
  javax.crypto.Cipher cipher = getCipher("bb5","1860", "17a74", "213f",false);
  String st=new String(cipher.doFinal(hexToByte(text))); 
  return st;
 }

 public static void main(String []str) throws Exception{
  String secretText="javalearning";
  String enSecretText=encrypt(secretText);

  System.out.println("\""+secretText+"\" after encryption---->"+enSecretText);

  String deSecretText=decrypt(enSecretText);
  System.out.println("After decryption --->"+deSecretText);
 }
}

Notes:

Check the main. It encodes the string "javalearning" and decode it back. 

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