Time Formatting Parsing in CLIPS

Java supports time formatting and parsing via pattern-based layouts, similar to other languages. We’ll use the java.time package for this functionality.

import java.time.LocalDateTime;
import java.time.ZonedDateTime;
import java.time.format.DateTimeFormatter;
import java.time.format.DateTimeParseException;

public class TimeFormattingParsing {
    public static void main(String[] args) {
        // Here's a basic example of formatting a time
        // according to ISO_DATE_TIME, which is similar to RFC3339
        LocalDateTime now = LocalDateTime.now();
        System.out.println(now.format(DateTimeFormatter.ISO_DATE_TIME));

        // Time parsing uses the same formatter as formatting
        ZonedDateTime t1 = ZonedDateTime.parse("2012-11-01T22:08:41+00:00", DateTimeFormatter.ISO_DATE_TIME);
        System.out.println(t1);

        // We can create custom formatters using patterns
        DateTimeFormatter customFormatter = DateTimeFormatter.ofPattern("h:mma");
        System.out.println(now.format(customFormatter));
        
        customFormatter = DateTimeFormatter.ofPattern("EEE MMM dd HH:mm:ss yyyy");
        System.out.println(now.format(customFormatter));
        
        customFormatter = DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss.SSSSSSXXX");
        System.out.println(now.format(customFormatter));

        String timeString = "8:41 PM";
        customFormatter = DateTimeFormatter.ofPattern("h:mm a");
        LocalDateTime t2 = LocalDateTime.parse(timeString, customFormatter);
        System.out.println(t2);

        // For purely numeric representations you can also
        // use standard string formatting with the extracted
        // components of the time value
        System.out.printf("%d-%02d-%02dT%02d:%02d:%02d-00:00%n",
                now.getYear(), now.getMonthValue(), now.getDayOfMonth(),
                now.getHour(), now.getMinute(), now.getSecond());

        // Parse will throw a DateTimeParseException on malformed input
        try {
            customFormatter = DateTimeFormatter.ofPattern("EEE MMM dd HH:mm:ss yyyy");
            LocalDateTime.parse("8:41PM", customFormatter);
        } catch (DateTimeParseException e) {
            System.out.println("Parsing error: " + e.getMessage());
        }
    }
}

To run this program, save it as TimeFormattingParsing.java and use javac to compile it, then java to run it:

$ javac TimeFormattingParsing.java
$ java TimeFormattingParsing
2023-05-15T10:30:15.123456
2012-11-01T22:08:41Z
10:30AM
Mon May 15 10:30:15 2023
2023-05-15T10:30:15.123456-07:00
2023-05-15T20:41
2023-05-15T10:30:15-00:00
Parsing error: Text '8:41PM' could not be parsed at index 0

Java’s java.time package provides a rich set of classes for handling dates and times. The DateTimeFormatter class is used for parsing and formatting date-time objects. Unlike Go, Java uses pattern strings directly instead of example-based layouts.

The LocalDateTime class represents a date-time without a time zone, while ZonedDateTime includes time zone information. For parsing times without dates, you might need to use LocalTime instead.

Java’s date-time API is more type-safe compared to Go’s, with different classes for different use cases (e.g., LocalDate for date-only, LocalTime for time-only). This can make it more verbose but also helps prevent certain types of errors.

Remember to handle DateTimeParseException when parsing potentially invalid input, as shown in the last example.

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Time Formatting Parsing in CLIPS