java.sql.Date - W3spoint

java.sql.Date is a class in the Java programming language that represents a date (year, month, and day) and provides functionality for working with dates. It extends the java.util.Date class and is used primarily for interacting with databases that store date information.

The java.sql.Date class represents a date in the SQL date format, which has a precision of one day. It does not store time or timezone information, only the year, month, and day. This class provides methods for comparing dates, formatting dates, and converting dates to and from strings.

One thing to note is that java.sql.Date is not the same as java.util.Date. While they both represent dates, they have different implementations and functionality. java.sql.Date is used primarily for database operations, while java.util.Date is used more generally for date manipulation and formatting.

java.sql.Date Constructor:

The java.sql.Date class has several constructors that allow you to create a new instance of the class with a specified date value. Here are the constructors:

Date(long date) – Creates a java.sql.Date object that represents the specified number of milliseconds since January 1, 1970, 00:00:00 GMT.
Date(int year, int month, int day) – Creates a java.sql.Date object that represents the specified year (minus 1900), month (0-11), and day (1-31).
Date(String s) – Creates a java.sql.Date object that represents the date specified by the string argument in the format “yyyy-[m]m-[d]d”, where yyyy is the year, mm is the month (1-12), and dd is the day of the month (1-31).

Note that the Date class does not support time or timezone information, so the constructors only take parameters for year, month, and day.

Here is an example of using the java.sql.Date constructors:

// Create a Date object for the current date
java.util.Date utilDate = new java.util.Date();
java.sql.Date sqlDate = new java.sql.Date(utilDate.getTime());

// Create a Date object for a specific date
java.sql.Date myDate = new java.sql.Date(2023-1900, 4, 7);

// Create a Date object from a string
java.sql.Date stringDate = java.sql.Date.valueOf("2023-05-07");

In the above example, we create a java.util.Date object for the current date, and then use its getTime() method to get the number of milliseconds since January 1, 1970, which is passed to the java.sql.Date constructor. We also create a java.sql.Date object for a specific date, and another one by parsing a string in the format “yyyy-[m]m-[d]d”.

java.sql.Date Methods:

The java.sql.Date class provides several methods that allow you to work with dates. Here are some of the most commonly used methods:

valueOf(String date) – Creates a java.sql.Date object from a string in the format “yyyy-[m]m-[d]d”.
toString() – Returns a string representation of the date in the format “yyyy-[m]m-[d]d”.
getTime() – Returns the number of milliseconds since January 1, 1970, 00:00:00 GMT.
compareTo(Date otherDate) – Compares this date to another date and returns 0 if they are equal, a value less than 0 if this date is before the other date, or a value greater than 0 if this date is after the other date.
equals(Object other) – Returns true if this date is equal to another object, which must be a java.sql.Date object.
valueOf(LocalDate localDate) – Creates a java.sql.Date object from a java.time.LocalDate object.
toLocalDate() – Returns a java.time.LocalDate object representing the same date as this java.sql.Date object.

Note that java.sql.Date is a subclass of java.util.Date, so it inherits many of its methods as well.

Here is an example of using some of these methods:

// Create a Date object for a specific date
java.sql.Date myDate = new java.sql.Date(2023-1900, 4, 7);

// Print the date in the format "yyyy-[m]m-[d]d"
System.out.println(myDate.toString());

// Create a LocalDate object from the Date object
java.time.LocalDate localDate = myDate.toLocalDate();

// Create a new Date object from the LocalDate object
java.sql.Date newDate = java.sql.Date.valueOf(localDate);

// Compare two dates
if (myDate.compareTo(newDate) == 0) {
    System.out.println("The two dates are equal");
} else if (myDate.compareTo(newDate) < 0) {
    System.out.println("The first date is before the second date");
} else {
    System.out.println("The first date is after the second date");
}

In the above example, we create a java.sql.Date object for a specific date and print it as a string. We then convert it to a java.time.LocalDate object using the toLocalDate() method, and then create a new java.sql.Date object from the LocalDate object using the valueOf() method. Finally, we compare the two dates using the compareTo() method to determine their relative order.

java.sql.Date Example: get current date:

Here’s an example of how to get the current date as a java.sql.Date object:

java.util.Date utilDate = new java.util.Date();
java.sql.Date sqlDate = new java.sql.Date(utilDate.getTime());
System.out.println("Current date: " + sqlDate.toString());

In the above example, we create a java.util.Date object for the current date using the no-argument constructor. We then create a new java.sql.Date object using the getTime() method of the java.util.Date object to get the number of milliseconds since January 1, 1970, 00:00:00 GMT, and pass it to the java.sql.Date constructor. Finally, we print the current date as a string using the toString() method.

Java String to java.sql.Date Example:

Here’s an example of how to convert a string in the format “yyyy-[m]m-[d]d” to a java.sql.Date object:

String dateString = "2023-05-07";
java.sql.Date sqlDate = java.sql.Date.valueOf(dateString);
System.out.println("Date as a java.sql.Date object: " + sqlDate.toString());

In the above example, we create a string variable dateString containing the date in the format “yyyy-[m]m-[d]d”. We then convert the string to a java.sql.Date object using the valueOf() method, which takes a string in the format “yyyy-[m]m-[d]d” as its argument. Finally, we print the resulting java.sql.Date object as a string using the toString() method.

java.sql.Date Example: void setTime()

The java.sql.Date class is immutable, meaning that once an object is created, its state cannot be changed. Therefore, there is no setTime() method for java.sql.Date.

However, if you need to change the time component of a java.sql.Date object, you can convert it to a java.util.Date object, modify the time component using setTime(), and then convert it back to a java.sql.Date object. Here’s an example:

// Create a Date object for a specific date
java.sql.Date myDate = new java.sql.Date(2023-1900, 4, 7);

// Convert the Date object to a util.Date object
java.util.Date utilDate = new java.util.Date(myDate.getTime());

// Set the time component to 12:00:00 PM
utilDate.setTime(utilDate.getTime() + (12 * 60 * 60 * 1000));

// Convert the util.Date object back to a sql.Date object
java.sql.Date newDate = new java.sql.Date(utilDate.getTime());

System.out.println("Original date: " + myDate.toString());
System.out.println("New date: " + newDate.toString());

In the above example, we create a java.sql.Date object for a specific date. We then convert it to a java.util.Date object using the getTime() method, modify the time component of the java.util.Date object using setTime(), and then convert it back to a java.sql.Date object using the java.sql.Date constructor. Finally, we print both the original and modified dates using the toString() method.

java.sql.Date Example: void toLocalDate()

The java.sql.Date class does not have a toLocalDate() method, as it is not part of the class’s API.

However, you can convert a java.sql.Date object to a java.time.LocalDate object using the toLocalDate() method of the java.sql.Date object’s toInstant() method. Here’s an example:

// Create a Date object for a specific date
java.sql.Date myDate = java.sql.Date.valueOf("2023-05-07");

// Convert the Date object to a LocalDate object
java.time.LocalDate localDate = myDate.toInstant().atZone(ZoneId.systemDefault()).toLocalDate();

System.out.println("Date as a LocalDate object: " + localDate.toString());

In the above example, we create a java.sql.Date object for a specific date. We then convert it to a java.time.LocalDate object using the toInstant() method to obtain an Instant object representing the same point on the time-line as the original java.sql.Date object, and the atZone() method to apply the default time-zone of the system to this instant, returning a ZonedDateTime. Finally, we convert this ZonedDateTime object to a java.time.LocalDate object using the toLocalDate() method. The resulting java.time.LocalDate object can be used to manipulate dates using the java.time API.

java.sql.Date Example: void toInstant()

The java.sql.Date class does not have a toInstant() method, as it is not part of the class’s API. However, you can convert a java.sql.Date object to a java.time.Instant object, which represents an instantaneous point on the time-line, using the toInstant() method of the java.sql.Date object. Here’s an example:

// Create a Date object for a specific date
java.sql.Date myDate = java.sql.Date.valueOf("2023-05-07");

// Convert the Date object to an Instant object
java.time.Instant instant = myDate.toInstant();

System.out.println("Date as an Instant object: " + instant.toString());

In the above example, we create a java.sql.Date object for a specific date. We then convert it to a java.time.Instant object using the toInstant() method. The resulting java.time.Instant object represents an instantaneous point on the time-line, and can be used to perform arithmetic and comparison operations using the java.time API. The toString() method of the Instant class returns a string representation of the instant in UTC.