[AES (acronym of Advanced Encryption Standard) is a symmetric encryption algorithm.

Encryption.java

import java.security.SecureRandom;

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

/**
  * <p>
 * [AES (acronym of Advanced Encryption Standard) is a symmetric encryption algorithm.
 * The algorithm was developed by two Belgian cryptographer Joan Daemen and Vincent Rijmen.
 * AES was designed to be efficient in both hardware and software, and supports a block length of 128 bits and key lengths of 128, 192, and 256 bits.]
 * more info: https://en.wikipedia.org/wiki/Advanced_Encryption_Standard
 */
public class Encryption {
/*
 * [How to use] ->
 * String encryptedText = Encryption.encrypt(masterpassword, simpletext) // get encrypted text from simple text
 * ...
 * String simpletext = Encryption.decrypt(masterpassword, encryptedText) // get simple text from encrypted text
 *
 *  */

    /**
     * This method use for encrypt plain text to hex
     *
     * @param masterPassword : master password for encrypt your text.Remember it for decryption process
     * @param simpletext     : this is plainText which you want to decrypt
     */
    public static String encrypt(String masterPassword, String simpletext) throws Exception {
        byte[] rawKey = getRawKey(masterPassword.getBytes());
        byte[] result = encrypt(rawKey, simpletext.getBytes());
        return toHex(result);
    }

    /**
     * This method use for decrypt hex text to plain text
     *
     * @param masterPassword : master password for decryption your text.Master password which you are used at time of encryption
     * @param encryptedText  : this is encryptedText which you encrypt
     */
    public static String decrypt(String masterPassword, String encryptedText) throws Exception {
        byte[] rawKey = getRawKey(masterPassword.getBytes());
        byte[] enc = toByte(encryptedText);
        byte[] result = decrypt(rawKey, enc);
        return new String(result);
    }

    private static byte[] getRawKey(byte[] seed) throws Exception {
        KeyGenerator keyGenerator = KeyGenerator.getInstance("AES");
        SecureRandom sr = SecureRandom.getInstance("SHA1PRNG");
        sr.setSeed(seed);
        keyGenerator.init(128, sr); // 192 and 256 bits may not be available
        SecretKey skey;
        skey = keyGenerator.generateKey();
        return skey.getEncoded();
    }


    private static byte[] encrypt(byte[] raw, byte[] clear) throws Exception {
        SecretKeySpec secretKeySpec = new SecretKeySpec(raw, "AES");
        Cipher cipher = Cipher.getInstance("AES");
        cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec);
        return cipher.doFinal(clear);
    }

    private static byte[] decrypt(byte[] raw, byte[] encrypted) throws Exception {
        SecretKeySpec secretKeySpec = new SecretKeySpec(raw, "AES");
        Cipher cipher = Cipher.getInstance("AES");
        cipher.init(Cipher.DECRYPT_MODE, secretKeySpec);
        return cipher.doFinal(encrypted);
    }

    /**
     * This method use for simple text to hex text
     *
     * @param text : text to converting into hex
     */
    public static String toHex(String text) {
        return toHex(text.getBytes());
    }

    /**
     * This method use for hex text to simple text
     *
     * @param hex : hex to converting into plaint text
     */
    public static String fromHex(String hex) {
        return new String(toByte(hex));
    }

    /**
     * This method use for hex text to byte
     */
    public static byte[] toByte(String hexString) {
        int len = hexString.length() / 2;
        byte[] result = new byte[len];
        for (int i = 0; i < len; i++)
            result[i] = Integer.valueOf(hexString.substring(2 * i, 2 * i + 2), 16).byteValue();
        return result;
    }

    /**
     * This method use for byte to hex
     */
    public static String toHex(byte[] buf) {
        if (buf == null)
            return "";
        StringBuffer result = new StringBuffer(2 * buf.length);
        for (byte aBuf : buf) {
            appendHex(result, aBuf);
        }
        return result.toString();
    }

    private final static String HEX = "0123456789ABCDEF";

    private static void appendHex(StringBuffer sb, byte b) {
        sb.append(HEX.charAt((b >> 4) & 0x0f)).append(HEX.charAt(b & 0x0f));
    }

}