The following code snippet is an example on how to generate SHA 256 hash of a String in Java

public String generateHash(String value) {
  String password=null;
   try {
	byte[] valueBytes = value.getBytes("UTF-8");
	MessageDigest md = MessageDigest.getInstance("SHA-256");
	byte[] encodedBytes = md.digest(valueBytes);
	String hexEncodedValue =  toHexString(encodedBytes);
	password = hexEncodedValue;
	} catch (UnsupportedEncodingException e) {
			//should not happen, just log.
			log.error(e.getMessage(), e);
	} catch (NoSuchAlgorithmException e) {
			//should not happen, just log.
			log.error(e.getMessage(), e);
	}
	return password;
}
/**
 * Fast convert a byte array to a hex string
 * with possible leading zero.
 * @param b array of bytes to convert to string
 * @return hex representation, two chars per byte.
 */

public static String toHexString (byte[] b)	{
  StringBuffer sb = new StringBuffer(b.length * 2);
	   for (int i=0; i < b.length; i++) {
		// look up high nibble char
		sb.append(hexChar[( b[i] & 0xf0) >>> 4]);
	        // look up low nibble char
	        sb.append(hexChar[b[i] & 0x0f]);
       }
	   return sb.toString();
}

	/**
	 * table to convert a nibble to a hex char.
	 */

	static char[] hexChar = {
	   '0' , '1' , '2' , '3' ,
	   '4' , '5' , '6' , '7' ,
	   '8' , '9' , 'a' , 'b' ,
	   'c' , 'd' , 'e' , 'f'};