How to check if a date is greater than another in Java?

I am working on a Java application which generates a report for a duration entered by a user in the command line. The user needs to enter the dates in the following format: dd-MM-yyyy

> java report startDate endDate

Example:

java report 01-01-2013 31-03-2013

In the code I save the dates in two strings. I have to make sure that the start date entered by the user should be a date earlier than the end-date. Is there an built-in function which can help me achieve this by passing these two strings to it?

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小开

You need to use a SimpleDateFormat (dd-MM-yyyy will be the format) to parse the 2 input strings to Date objects and then use the Date#before(otherDate) (or) Date#after(otherDate) to compare them.

Try to implement the code yourself.

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最佳答案

You can use Date.before() or Date.after() or Date.equals() for date comparison.

Taken from here:

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


public class DateDiff {


public static void main( String[] args )
{
compareDates("2017-01-13 00:00:00", "2017-01-14 00:00:00");// output will be Date1 is before Date2
compareDates("2017-01-13 00:00:00", "2017-01-12 00:00:00");//output will be Date1 is after Date2
compareDates("2017-01-13 00:00:00", "2017-01-13 10:20:30");//output will be Date1 is before Date2 because date2 is ahead of date 1 by 10:20:30 hours
compareDates("2017-01-13 00:00:00", "2017-01-13 00:00:00");//output will be Date1 is equal Date2 because both date and time are equal
}


public static void compareDates(String d1,String d2)
{
try{
// If you already have date objects then skip 1


//1
// Create 2 dates starts
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
Date date1 = sdf.parse(d1);
Date date2 = sdf.parse(d2);


System.out.println("Date1"+sdf.format(date1));
System.out.println("Date2"+sdf.format(date2));System.out.println();


// Create 2 dates ends
//1


// Date object is having 3 methods namely after,before and equals for comparing
// after() will return true if and only if date1 is after date 2
if(date1.after(date2)){
System.out.println("Date1 is after Date2");
}
// before() will return true if and only if date1 is before date2
if(date1.before(date2)){
System.out.println("Date1 is before Date2");
}


//equals() returns true if both the dates are equal
if(date1.equals(date2)){
System.out.println("Date1 is equal Date2");
}


System.out.println();
}
catch(ParseException ex){
ex.printStackTrace();
}
}


public static void compareDates(Date date1,Date date2)
{
// if you already have date objects then skip 1
//1


//1


//date object is having 3 methods namely after,before and equals for comparing
//after() will return true if and only if date1 is after date 2
if(date1.after(date2)){
System.out.println("Date1 is after Date2");
}


//before() will return true if and only if date1 is before date2
if(date1.before(date2)){
System.out.println("Date1 is before Date2");
}


//equals() returns true if both the dates are equal
if(date1.equals(date2)){
System.out.println("Date1 is equal Date2");
}


System.out.println();
}
}
小开

Parse the two dates firstDate and secondDate using SimpleDateFormat.

firstDate.after(secondDate);

firstDate.before(secondDate);

小开

Parse the string into date, then compare using compareTo, before or after

Date d = new Date();
d.compareTo(anotherDate)

i.e 

Date date1 = new SimpleDateFormat("MM/dd/yyyy").parse(date1string)
Date date2 = new SimpleDateFormat("MM/dd/yyyy").parse(date2string)


date1.compareTo(date2);

Copying the comment provided below by @MuhammadSaqib to complete this answer.

Returns the value 0 if the argument Date is equal to this Date; a value less than 0 if this Date is before the Date argument, and a value greater than 0 if this Date is after the Date argument. and NullPointerException - if anotherDate is null.

javadoc for compareTo http://docs.oracle.com/javase/6/docs/api/java/util/Date.html#compareTo(java.util.Date)


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