使用SimpleDateFormat，规定好格式，parser出错即为非法/** * Calculates the number of days between two calendar days in a manner * which is independent of the Calendar type used. * * @param d1 The first date. * @param d2 The second date. * * @return The number of days between the two dates. Zero is * returned if the dates are the same, one if the dates are * adjacent, etc. The order of the dates * does not matter, the value returned is always >= 0. * If Calendar types of d1 and d2 * are different, the result may not be accurate. */static int getDaysBetween (java.util.Calendar d1, java.util.Calendar d2) { if (d1.after(d2)) { // swap dates so that d1 is start and d2 is end java.util.Calendar swap = d1; d1 = d2; d2 = swap; } int days = d2.get(java.util.Calendar.DAY_OF_YEAR) - d1.get(java.util.Calendar.DAY_OF_YEAR); int y2 = d2.get(java.util.Calendar.YEAR); if (d1.get(java.util.Calendar.YEAR) != y2) { d1 = (java.util.Calendar) d1.clone(); do { days += d1.getActualMaximum(java.util.Calendar.DAY_OF_YEAR); d1.add(java.util.Calendar.YEAR, 1); } while (d1.get(java.util.Calendar.YEAR) != y2); } return days;}