question: public static String byte2Hex ( int value ) { if ( value > 255 || value < 0 ) { throw new IllegalArgumentException ( "The int converting to hex should be in range 0~255" ) ; } return String . valueOf ( FIRST_CHAR [ value ] ) + String . valueOf ( SECOND_CHAR [ value ] ) ; }
target:  Convert an int [0-255] to a hexadecimal string representation.