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

Source: Internet
Author: User
Tags date1

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}

 

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