Java date comparison, date calculation, and java date comparison Calculation

Java date comparison, date calculation, and java date comparison Calculation

They are common comparison methods between dates for future reference.

Warm-up: Get the current time

SimpleDateFormat df = new SimpleDateFormat ("yyyy-MM-dd HH: mm: ss"); // you can specify the date format.
String nowDate = df. format (new Date (); // new Date () is used to obtain the current system time.

Note: The landlord always thinks that the date type is not as good as the string type, so the following comparison is a string type date for comparison. If you are really stubborn, OK, the following is the method to convert date to string:

SimpleDateFormat df = new SimpleDateFormat ("yyyy-MM-dd HH: mm: ss"); // you can specify the date format.
String date = df. format (time of Date type );

1. Compare the size of two string-type dates

1 public static int compare_date (String DATE1, String DATE2) {2 DateFormat df = new SimpleDateFormat ("yyyy-MM-dd HH: mm: ss "); 3 try {4 Date dt1 = df. parse (DATE1); 5 Date dt2 = df. parse (DATE2); 6 if (dt1.getTime ()> dt2.getTime () {7 System. out. println ("dt1 before dt2"); 8 return 1; 9} else if (dt1.getTime () <dt2.getTime () {10 System. out. println ("dt1 after dt2"); 11 return-1; 12} else {13 return 0; 14} 15} catch (Exception exception) {16 Exception. printStackTrace (); 17} 18 return 0; 19}

2. returns the number of days between two string-type dates.

 1  public static int daysBetween(String smdate,String bdate){   2          SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd");   3          Calendar cal = Calendar.getInstance();     4          long time1 = 0; 5          long time2 = 0; 6           7          try{ 8               cal.setTime(sdf.parse(smdate));    9               time1 = cal.getTimeInMillis();    10               cal.setTime(sdf.parse(bdate)); 11               time2 = cal.getTimeInMillis();  12          }catch(Exception e){13              e.printStackTrace();14          }15          long between_days=(time2-time1)/(1000*3600*24);  16              17         return Integer.parseInt(String.valueOf(between_days));     18      }  

3. Return the hours of two string-type date differences

 1  public static int daysBetween2(String startTime, String endTime) { 2           SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd HH");   3           Calendar cal = Calendar.getInstance();     4           long time1 = 0; 5           long time2 = 0; 6            7           try{ 8                cal.setTime(sdf.parse(startTime));    9                time1 = cal.getTimeInMillis();    10                cal.setTime(sdf.parse(endTime)); 11                time2 = cal.getTimeInMillis();  12           }catch(Exception e){13               e.printStackTrace();14           }15           long between_days=(time2-time1)/(1000*3600);  16               17          return Integer.parseInt(String.valueOf(between_days));     18       }

4. Calculate the coincidence date of the two segments

1/** 2 * calculate the coincidence date of the two dates 3 * @ param str1 start date 1 4 * @ param str2 end date 1 5 * @ param str3 start date 2 6 *@ param str4 end date 2 7 * @ return 8 * @ throws Exception 9 */10 public static Map <String, object> comparisonRQ (String str1, String str2, String str3, 11 String str4) throws Exception {12 String mesg = ""; 13 DateFormat df = new SimpleDateFormat ("yyyy-MM-dd"); 14 String startdate = ""; 15 String enddate = ""; 16 try {17 Date dt1 = df. parse (str1); 18 Date dt2 = df. parse (str2); 19 Date dt3 = df. parse (str3); 20 Date dt4 = df. parse (str4); 21 if (dt1.getTime () <= dt3.getTime () & dt3.getTime () <= dt2.getTime () & dt2.getTime () <= dt4.getTime ()) {22 mesg = "f"; // coincidence 23 startdate = str3; 24 enddate = str2; 25} 26 if (dt1.getTime () >= dt3.getTime () & dt3.getTime () <= dt2.getTime () & dt2.getTime () <= dt4.getTime () {27 mesg = "f"; // coincidence 28 startdate = str1; 29 enddate = str2; 30} 31 32 if (dt3.getTime () <= dt1.getTime () & dt1.getTime () <= dt4.getTime () & dt4.getTime () <= dt2.getTime ()) {33 mesg = "f"; // coincidence 34 startdate = str1; 35 enddate = str4; 36} 37 if (dt3.getTime () >= dt1.getTime () & dt1.getTime () <= dt4.getTime () & dt4.getTime () <= dt2.getTime () {38 mesg = "f"; // coincidence 39 startdate = str3; 40 enddate = str4; 41} 42 43 System. out. println (startdate + "----" + enddate); 44 45 46} catch (ParseException e) {47 e. printStackTrace (); 48 throw new ParseException (e. getMessage (), 0); 49} catch (Exception e) {50 e. printStackTrace (); 51 throw new Exception (e); 52} 53 Map <String, Object> map = new HashMap <String, Object> (); 54 map. put ("startdate", startdate); 55 map. put ("enddate", enddate); 56 return map; 57}