Unable to obtain LocalDateTime from TemporalAccessor when parsing LocalDateTime (Java 8)

Parsing the Date

Resist the temptation to use LocalDateTime for date-only strings as LocalDateTime requires time information too. Instead, consider LocalDate for parsing dates:

DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyyMMdd");
LocalDate localDate = LocalDate.parse("20230401", formatter); /* Time machine activated, enjoy 2023 ;) */
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Need to transform your LocalDate to LocalDateTime? We got you covered! Use .atStartOfDay() for a seamless journey to LocalDateTime:

LocalDateTime localDateTime = localDate.atStartOfDay(); // Returns LocalDateTime at 00:00:00
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Advanced Parsing: DateTimeFormatterBuilder

Sometimes your date strings could include time and sometimes not. In these precarious situations, employ our pal DateTimeFormatterBuilder and its sidekick parseDefaulting. They'll provide default values for the missing time components.

Robust Custom Patterns

Precision is key when defining custom patterns with DateTimeFormatter.ofPattern. Remember, literals and case sensitivity count!

DateTimeFormatter customFormatter = new DateTimeFormatterBuilder()
        .appendPattern("yyyy-MM-dd")
        .optionalStart()
        .appendPattern("'T'HH:mm:ss")
        .optionalEnd()
        .toFormatter(); // Your own custom transformer!

LocalDateTime parsedDateTime = LocalDateTime.parse("2023-04-01T13:45:30", customFormatter);
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The use of optionalStart() and optionalEnd() shields you from pattern variance.

It's Try-catch Time!

Now here's a PSA: DateTimeParseException doesn't take prisoners. Instead of watching your program implode, wrap your parse process in a civil try-catch block:

try {
    LocalDateTime.parse(yourDateString, yourFormatter); /* Fingers crossed! */
} catch (DateTimeParseException e) {
    System.err.println("Oops, error parsing the date-time: " + e.getMessage()); /* e stands for 'Expect the Unexpected'! */
    // More error handling? You bet!
}
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Mr. Hyde: Common Pitfalls

Here are some areas to watch out for when working with LocalDateTime:

1. 24-hour vs. 12-hour confusion: Precision in formatter is vital.
2. Syntax surprises: Every character matters in the pattern!
3. Update JDK: Outdated JDK might lead to unforeseen issues.
4. Documentation matters: When in doubt, turn to official Java Docs or relevant threads.

Special Cases, Anyone?

Finally, take the following goodies home for those unknown-unknowns:

1. Time Zones: Use ZonedDateTime for timezone aware timestamps.
2. Internationalization: Call DateTimeFormatter.withLocale(Locale) for locale-sensitive times.
3. Bulk Testing: Validate your formatter against diverse date-time formats.