//format pattern
String pattern = "yyyy-MM-dd HH:mm:ss";
SimpleDateFormat formater = new SimpleDateFormat(pattern);

//Date -> String :
Date date1 = new Date();
String str1 = formater.format(date1);

//String ->Date
String str2 = "2003-10-18 13:15:45";
Date date2 = formater.parse(str2);