Example Scenario

Consider a date and time of May 6, 2022, represented as 05/06/2022 12:06:22. The individual resides in the GMT timezone, and the objective is to convert this date to the Singapore timezone (GMT+8), resulting in 06-05-2022 20:06:22. Essentially, we are tasked with transforming a given string into another string formatted for the specified timezone.

The following sections will outline the process and relevant classes utilized in this conversion.

Step 1: Define Input Format and Set Timezone

final String date = "05/06/2022 12:06:22";

final String dateFormat = "MM/dd/yyyy HH:mm:ss";

final SimpleDateFormat inputDateFormat = new SimpleDateFormat(dateFormat);

inputDateFormat.setTimeZone(TimeZone.getTimeZone("GMT"));

To begin, we create a SimpleDateFormat object that accepts the input string. It is crucial to specify not just the string format but also the timezone for the input time. Available timezones can be obtained using TimeZone.getAvailableIDs. In this scenario, we will use GMT to define the input timezone.

Step 2: Specify Target Timezone

String timezone = "Singapore";

In addition to using TimeZone, we can employ ZoneId to denote the desired timezone. A list of Java-supported ZoneIds can be accessed via ZoneId.getAvailableZoneIds, enabling us to confirm the Singapore timezone.

Step 3: Generate LocalDateTime Object

LocalDateTime localDateTime = inputDateFormat.parse(date) //Date

.toInstant() //Instant

.atZone(ZoneId.of(timezone)) //ZonedDateTime

.toLocalDateTime(); // LocalDateTime

Initially, we parse the date using the inputDateFormat, yielding a Date object. This object is then converted to an Instant object, which represents a precise moment on the Java timeline. Next, we use the Instant object to derive the ZonedDateTime according to the specified timezone, ultimately converting it into a LocalDateTime object.

Step 4: Convert LocalDateTime to String

final Date targetDateTime = Timestamp.valueOf(localDateTime);

final String result = new SimpleDateFormat("dd-MM-yyyy HH:mm:ss").format(targetDateTime);

Since SimpleDateFormat requires a Date object, we can leverage java.sql.Timestamp to revert the LocalDateTime object back to a Date object. This enables us to format the final string output using SimpleDateFormat.

Test Output

The following illustrates the outcome of the program, demonstrating the correct time conversion and the desired string format.

A Simpler Method

An alternative, more straightforward approach utilizes only SimpleDateFormat:

final String inDateFormat = "MM/dd/yyyy HH:mm:ss";

final SimpleDateFormat inDateFormatter = new SimpleDateFormat(inDateFormat);

inDateFormatter.setTimeZone(TimeZone.getTimeZone("GMT"));

Date dateTime = inDateFormatter.parse(date);

final String outDateFormat = "dd-MM-yyyy HH:mm:ss";

final SimpleDateFormat outDateFormatter = new SimpleDateFormat(outDateFormat);

outDateFormatter.setTimeZone(TimeZone.getTimeZone("Singapore"));

String result2 = outDateFormatter.format(dateTime);

Test Result:

The output remains consistent with the previous example.

In conclusion, this article aims to enhance your understanding of Java's datetime classes. If you're passionate about technology and wish to explore similar topics, consider following my channel for ongoing insights and inspirations.

Additional Resources:

• How to Implement Deep Copy of an Object in Java
• How to Auto-Generate Repetitive Java Code to Save Time

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