How to check Date Null in Java?
In this section, we will be acknowledged about Date Null in Java. The date null in Java is an entity that is used when there is no specified value for a date. Since we are not supposed to leave it empty, we would declare date as null.
Introduction
Let discuss an instance where the real time application is described.
If you are working on a class called person, DateOfBirth is one of the person’s fields, however you are unsure of how to treat dates that are uncertain. You have been utilizing java.time up to this point. You have been instantiating the field dateOfBirth’s LocalDate to null upon instantiation. This isn’t ideal because attempting to match dateOfBirth to other dates, like the LocalDate.now, causes null pointer exceptions ().
What is the most ideal method for dealing with dateOfBirth? You’re just going to make a brand-new class and handle ambiguous dates internally, right? Or is there a more effective method? Since LocalDate is immutable, you can’t simply expand it; you must go to the source instead.
The LocalDate is unboxed by get(), but if you don’t have any LocalDates, it throws a NoSuchElementException. Like the dreaded NullPointerException, it is sadly an unchecked exception. Consequently, I would advise against adopting this technique.
When you want to only run certain code if you’ve had a value and leave everything else alone, the construct ifPresent(Consumer? super T> consumer) seems helpful.
orElseThrow(exception) which throws said exception when you don’t have a value. The exception can (and should be) a checked exception so you are forced to handle it.
If you don’t have any values, orElse(T value) returns the fake value you supplied instead of unboxing the value.
The following is the solution for such an instance, it would absolutely work best
Class Optional
In Java 8, a handy container class was introduced. It serves as a wrapper for values that you may or might not be familiar with. It is unboxed with a variety of techniques that all let you gracefully handle the situation where the value is unknown.
an object that serves as a container and may or may not hold a non-null value. Get() will yield the value and isPresent() would return true if a component is present.
Additional methods that rely on the existence or absence of a contained value are offered, including ifPresent() and orElse() (which returns a default value in the absence of a value)
Since this is a value-based class, it is best to avoid using identity-sensitive operations (such as referencing equality (==), identity hashing, or synchronization) on instances of Optional due to the possibility of unexpected outcomes.
You should just use null as an appropriate response in the scope of the database because we have it and it is commonly recognized across datastores.
There are probably two ways to generate the output
Let us know the algorithm of how they function
By using if-else statements
The leverage of the if-else statements would be as follows
By using (=) operator
The leverage of the (=) operator to predict if the date is null or not null is as follows
Either this way or as follows
Now let us write a program that uses both the techniques and prints the output. I make sure the example program does not go complex.
// Java program that depicts if the date is null or not null using equals() and (=) import java.io.*; import java.util.*; class Null < public static void main( String[] args ) < Date date = showDate(); //check with if-else statement with equals() if ( !date.equals( null ) ) < System.out.println( "NOT NULL" ); >else < System.out.println( "NULL" ); >//check with if-else statement with = operator if ( date!= null ) < System.out.println( "NOT NULL" ); >else < System.out.println( "NULL" ); >> public static Date showDate() < return new Date(); >> Java util date is null
The class Date represents a specific instant in time, with millisecond precision. Prior to JDK 1.1, the class Date had two additional functions. It allowed the interpretation of dates as year, month, day, hour, minute, and second values. It also allowed the formatting and parsing of date strings. Unfortunately, the API for these functions was not amenable to internationalization. As of JDK 1.1, the Calendar class should be used to convert between dates and time fields and the DateFormat class should be used to format and parse date strings. The corresponding methods in Date are deprecated. Although the Date class is intended to reflect coordinated universal time (UTC), it may not do so exactly, depending on the host environment of the Java Virtual Machine. Nearly all modern operating systems assume that 1 day = 24 × 60 × 60 = 86400 seconds in all cases. In UTC, however, about once every year or two there is an extra second, called a «leap second.» The leap second is always added as the last second of the day, and always on December 31 or June 30. For example, the last minute of the year 1995 was 61 seconds long, thanks to an added leap second. Most computer clocks are not accurate enough to be able to reflect the leap-second distinction. Some computer standards are defined in terms of Greenwich mean time (GMT), which is equivalent to universal time (UT). GMT is the «civil» name for the standard; UT is the «scientific» name for the same standard. The distinction between UTC and UT is that UTC is based on an atomic clock and UT is based on astronomical observations, which for all practical purposes is an invisibly fine hair to split. Because the earth’s rotation is not uniform (it slows down and speeds up in complicated ways), UT does not always flow uniformly. Leap seconds are introduced as needed into UTC so as to keep UTC within 0.9 seconds of UT1, which is a version of UT with certain corrections applied. There are other time and date systems as well; for example, the time scale used by the satellite-based global positioning system (GPS) is synchronized to UTC but is not adjusted for leap seconds. An interesting source of further information is the United States Naval Observatory (USNO):
- A year y is represented by the integer y — 1900 .
- A month is represented by an integer from 0 to 11; 0 is January, 1 is February, and so forth; thus 11 is December.
- A date (day of month) is represented by an integer from 1 to 31 in the usual manner.
- An hour is represented by an integer from 0 to 23. Thus, the hour from midnight to 1 a.m. is hour 0, and the hour from noon to 1 p.m. is hour 12.
- A minute is represented by an integer from 0 to 59 in the usual manner.
- A second is represented by an integer from 0 to 61; the values 60 and 61 occur only for leap seconds and even then only in Java implementations that actually track leap seconds correctly. Because of the manner in which leap seconds are currently introduced, it is extremely unlikely that two leap seconds will occur in the same minute, but this specification follows the date and time conventions for ISO C.
In all cases, arguments given to methods for these purposes need not fall within the indicated ranges; for example, a date may be specified as January 32 and is interpreted as meaning February 1.
Constructor Summary
Allocates a Date object and initializes it so that it represents the time at which it was allocated, measured to the nearest millisecond.
As of JDK version 1.1, replaced by Calendar.set(year + 1900, month, date) or GregorianCalendar(year + 1900, month, date) .
As of JDK version 1.1, replaced by Calendar.set(year + 1900, month, date, hrs, min) or GregorianCalendar(year + 1900, month, date, hrs, min) .
As of JDK version 1.1, replaced by Calendar.set(year + 1900, month, date, hrs, min, sec) or GregorianCalendar(year + 1900, month, date, hrs, min, sec) .
Allocates a Date object and initializes it to represent the specified number of milliseconds since the standard base time known as «the epoch», namely January 1, 1970, 00:00:00 GMT.
Class Date
Prior to JDK 1.1, the class Date had two additional functions. It allowed the interpretation of dates as year, month, day, hour, minute, and second values. It also allowed the formatting and parsing of date strings. Unfortunately, the API for these functions was not amenable to internationalization. As of JDK 1.1, the Calendar class should be used to convert between dates and time fields and the DateFormat class should be used to format and parse date strings. The corresponding methods in Date are deprecated.
Although the Date class is intended to reflect coordinated universal time (UTC), it may not do so exactly, depending on the host environment of the Java Virtual Machine. Nearly all modern operating systems assume that 1 day = 24 × 60 × 60 = 86400 seconds in all cases. In UTC, however, about once every year or two there is an extra second, called a «leap second.» The leap second is always added as the last second of the day, and always on December 31 or June 30. For example, the last minute of the year 1995 was 61 seconds long, thanks to an added leap second. Most computer clocks are not accurate enough to be able to reflect the leap-second distinction.
Some computer standards are defined in terms of Greenwich mean time (GMT), which is equivalent to universal time (UT). GMT is the «civil» name for the standard; UT is the «scientific» name for the same standard. The distinction between UTC and UT is that UTC is based on an atomic clock and UT is based on astronomical observations, which for all practical purposes is an invisibly fine hair to split. Because the earth’s rotation is not uniform (it slows down and speeds up in complicated ways), UT does not always flow uniformly. Leap seconds are introduced as needed into UTC so as to keep UTC within 0.9 seconds of UT1, which is a version of UT with certain corrections applied. There are other time and date systems as well; for example, the time scale used by the satellite-based global positioning system (GPS) is synchronized to UTC but is not adjusted for leap seconds. An interesting source of further information is the United States Naval Observatory (USNO):
and the material regarding «Systems of Time» at:
which has descriptions of various different time systems including UT, UT1, and UTC.
- A year y is represented by the integer y — 1900 .
- A month is represented by an integer from 0 to 11; 0 is January, 1 is February, and so forth; thus 11 is December.
- A date (day of month) is represented by an integer from 1 to 31 in the usual manner.
- An hour is represented by an integer from 0 to 23. Thus, the hour from midnight to 1 a.m. is hour 0, and the hour from noon to 1 p.m. is hour 12.
- A minute is represented by an integer from 0 to 59 in the usual manner.
- A second is represented by an integer from 0 to 61; the values 60 and 61 occur only for leap seconds and even then only in Java implementations that actually track leap seconds correctly. Because of the manner in which leap seconds are currently introduced, it is extremely unlikely that two leap seconds will occur in the same minute, but this specification follows the date and time conventions for ISO C.
In all cases, arguments given to methods for these purposes need not fall within the indicated ranges; for example, a date may be specified as January 32 and is interpreted as meaning February 1.
Constructor Summary
Allocates a Date object and initializes it so that it represents the time at which it was allocated, measured to the nearest millisecond.
As of JDK version 1.1, replaced by Calendar.set(year + 1900, month, date) or GregorianCalendar(year + 1900, month, date) .
As of JDK version 1.1, replaced by Calendar.set(year + 1900, month, date, hrs, min) or GregorianCalendar(year + 1900, month, date, hrs, min) .
As of JDK version 1.1, replaced by Calendar.set(year + 1900, month, date, hrs, min, sec) or GregorianCalendar(year + 1900, month, date, hrs, min, sec) .
Allocates a Date object and initializes it to represent the specified number of milliseconds since the standard base time known as «the epoch», namely January 1, 1970, 00:00:00 GMT.