Date Comparison using Java

Question

I have two dates:

1. toDate (user input in MM/dd/yyyy format)
2. currentDate (obtained by new Date())

I need to compare the currentDate with toDate. I have to display a report only when the toDate is equal to or more than currentDate. How can I do that?

Answer 1

Date#equals() and Date#after()

If there is a possibility that the hour and minute fields are != 0, you'd have to set them to 0.

I can't forget to mention that using java.util.Date is considered a bad practice, and most of its methods are deprecated. Use java.util.Calendar or JodaTime, if possible.

Answer 2

Use java.util.Calendar if you have extensive date related processing.

Date has before(), after() methods. you could use them as well.

Answer 3

You are probably looking for:

!toDate.before(currentDate)

before() and after() test whether the date is strictly before or after. So you have to take the negation of the other one to get non strict behaviour.

Answer 4

it is easier to compare dates using the java.util.Calendar . Here is what you might do:

Calendar toDate = Calendar.getInstance();
        Calendar nowDate = Calendar.getInstance();
        toDate.set(<set-year>,<set-month>,<set-date->);  
        if(!toDate.before(nowDate))
        //display your report
        else
        // don't display the report

Answer 5

If you're set on using Java Dates rather than, say, JodaTime, use a java.text.DateFormat to convert the string to a Date, then compare the two using .equals:

I almost forgot: You need to zero out the hours, minutes, seconds, and milliseconds on the current date before comparing them. I used a Calendar object below to do it.

import java.text.DateFormat;
import java.util.Calendar;
import java.util.Date;

// Other code here
    String toDate;
    //toDate = "05/11/2010";

    // Value assigned to toDate somewhere in here

    DateFormat df = DateFormat.getDateInstance(DateFormat.SHORT);
    Calendar currDtCal = Calendar.getInstance();

    // Zero out the hour, minute, second, and millisecond
    currDtCal.set(Calendar.HOUR_OF_DAY, 0);
    currDtCal.set(Calendar.MINUTE, 0);
    currDtCal.set(Calendar.SECOND, 0);
    currDtCal.set(Calendar.MILLISECOND, 0);

    Date currDt = currDtCal.getTime();

    Date toDt;
    try {
        toDt = df.parse(toDate);
    } catch (ParseException e) {
        toDt = null;
        // Print some error message back to the user
    }

    if (currDt.equals(toDt)) {
        // They're the same date
    }

Answer 6

This is one of the ways:

String toDate = "05/11/2010";

if (new SimpleDateFormat("MM/dd/yyyy").parse(toDate).getTime() / (1000 * 60 * 60 * 24) >= System.currentTimeMillis() / (1000 * 60 * 60 * 24)) {
    System.out.println("Display report.");
} else {
    System.out.println("Don't display report.");
}

A bit more easy interpretable:

String toDateAsString = "05/11/2010";
Date toDate = new SimpleDateFormat("MM/dd/yyyy").parse(toDateAsString);
long toDateAsTimestamp = toDate.getTime();
long currentTimestamp = System.currentTimeMillis();
long getRidOfTime = 1000 * 60 * 60 * 24;
long toDateAsTimestampWithoutTime = toDateAsTimestamp / getRidOfTime;
long currentTimestampWithoutTime = currentTimestamp / getRidOfTime;

if (toDateAsTimestampWithoutTime >= currentTimestampWithoutTime) {
    System.out.println("Display report.");
} else {
    System.out.println("Don't display report.");
}

Oh, as a bonus, the JodaTime's variant:

String toDateAsString = "05/11/2010";
DateTime toDate = DateTimeFormat.forPattern("MM/dd/yyyy").parseDateTime(toDateAsString);
DateTime now = new DateTime();

if (!toDate.toLocalDate().isBefore(now.toLocalDate())) {
    System.out.println("Display report.");
} else {
    System.out.println("Don't display report.");
}

Answer 7

If for some reason you're intent on using Date objects for your solution, you'll need to do something like this:

    // Convert user input into year, month, and day integers
    Date toDate = new Date(year - 1900, month - 1, day + 1);
    Date currentDate = new Date();
    boolean runThatReport = toDate.after(currentDate);

Shifting the toDate ahead to midnight of the next day will take care of the bug I've whined about in the comments to other answers. But, note that this approach uses a deprecated constructor; any approach relying on Date will use one deprecated method or another, and depending on how you do it may lead to race conditions as well (if you base toDate off of new Date() and then fiddle around with the year, month, and day, for instance). Use Calendar, as described elsewhere.