question: public static String keyForImage ( String imagePath ) { String key = null ; try { MessageDigest messageDigest = MessageDigest . getInstance ( "md5" ) ; messageDigest . update ( imagePath . getBytes ( ) ) ; key = byteToHex ( messageDigest . digest ( ) ) ; } catch ( NoSuchAlgorithmException e ) { e . printStackTrace ( ) ; } return key ; }
target:  Generate md5 key for picture