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How to compare dates in Java

How to compare dates in Java

8:47:00 AM
1. Date.compareTo()
A classic method to compare two dates in Java.
– Return value is 0 if both dates are equal.
– Return value is greater than 0 , if Date is after the date argument.
– Return value is less than 0, if Date is before the date argument.


package com.mkyong.date;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;

public class App 
{
     public static void main( String[] args ) 
    {
     try{
      
      SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
         Date date1 = sdf.parse("2009-12-31");
         Date date2 = sdf.parse("2010-01-31");

         System.out.println(sdf.format(date1));
         System.out.println(sdf.format(date2));
         
         if(date1.compareTo(date2)>0){
          System.out.println("Date1 is after Date2");
         }else if(date1.compareTo(date2)<0){
          System.out.println("Date1 is before Date2");
         }else if(date1.compareTo(date2)==0){
          System.out.println("Date1 is equal to Date2");
         }else{
          System.out.println("How to get here?");
         }
         
     }catch(ParseException ex){
      ex.printStackTrace();
     }
    }
}
2. Date.before(), Date.after() and Date.equals()
A more user friendly method to compare two dates. Java developers seldom use this method, not really sure what may causing it, may be they just didn't aware of it?

package com.mkyong.date;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;

public class App 
{
    public static void main( String[] args ) 
    {
     try{
      
      SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
         Date date1 = sdf.parse("2009-12-31");
         Date date2 = sdf.parse("2010-01-31");

         System.out.println(sdf.format(date1));
         System.out.println(sdf.format(date2));
         
         if(date1.after(date2)){
          System.out.println("Date1 is after Date2");
         }
         
         if(date1.before(date2)){
          System.out.println("Date1 is before Date2");
         }
         
         if(date1.equals(date2)){
          System.out.println("Date1 is equal Date2");
         }
         
     }catch(ParseException ex){
      ex.printStackTrace();
     }
    }
}
3. Calender.before(), Calender.after() and Calender.equals()
Most common way to compare two dates with Calendar object, and believe it's most widely used method. 
package com.mkyong.date;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

public class App 
{
     public static void main( String[] args ) 
    {
     try{
      
      SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
         Date date1 = sdf.parse("2009-12-31");
         Date date2 = sdf.parse("2010-01-31");

         System.out.println(sdf.format(date1));
         System.out.println(sdf.format(date2));
         
         Calendar cal1 = Calendar.getInstance();
         Calendar cal2 = Calendar.getInstance();
         cal1.setTime(date1);
         cal2.setTime(date2);
         
         if(cal1.after(cal2)){
          System.out.println("Date1 is after Date2");
         }
         
         if(cal1.before(cal2)){
          System.out.println("Date1 is before Date2");
         }
         
         if(cal1.equals(cal2)){
          System.out.println("Date1 is equal Date2");
         }
         
     }catch(ParseException ex){
      ex.printStackTrace();
     }
    }
}

nguồn : http://www.mkyong.com/java/how-to-compare-dates-in-java/