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The article explains that in Java's SimpleDateFormat the lowercase y pattern (year‑of‑era) should be used for calendar dates, because the uppercase Y pattern represents a week‑based year which can incorrectly roll over to the next year near year‑end, causing bugs.
This article explains how using 'YYYY' instead of 'yyyy' in Java's SimpleDateFormat can cause year miscalculations, especially around year-end weeks, demonstrates the issue with sample code, shows correct usage, and warns developers to avoid this subtle bug.
This article presents several common solutions for addressing the thread‑safety problem of Java's SimpleDateFormat in high‑concurrency environments, including using local variables, synchronized blocks, Lock, ThreadLocal, Java 8 DateTimeFormatter, and Joda‑Time, and evaluates their performance and suitability.
This article explains why Java's SimpleDateFormat is not thread‑safe, demonstrates the concurrency problem with a multithreaded demo, and presents three solutions—creating new instances, synchronizing access, and using ThreadLocal—highlighting the ThreadLocal approach with code examples and discussion of potential memory‑leak considerations.
This article compares three common Java date‑time formatting approaches—SimpleDateFormat, Java 8’s DateTimeFormatter, and Apache Commons Lang3’s DateFormatUtils—examines thread‑safety issues, provides code examples, and offers conversion utilities between Date, LocalDate, and LocalDateTime for robust backend development.
This article explains why SimpleDateFormat.parse() and SimpleDateFormat.format() are not thread‑safe in Java, analyzes the underlying causes involving shared Calendar objects, and presents three practical solutions—including per‑thread instances, synchronized blocks, and ThreadLocal usage—to eliminate concurrency bugs.
This article explains the subtle difference between 'yyyy' and 'YYYY' in Java's SimpleDateFormat, demonstrates how using the wrong pattern can cause year miscalculations—especially on December 31st—and provides code examples and a clear explanation to help developers avoid this common bug.
The article explains how using the week‑based year pattern (YYYY) instead of the calendar year pattern (yyyy) in Java's SimpleDateFormat can cause dates like 2019‑12‑31 to be displayed as 2020‑12‑31, illustrating the issue with code examples and a clear explanation of the underlying rules.
This article explains why SimpleDateFormat is not thread‑safe in Java, demonstrates the problem with multithreaded examples, and presents five practical solutions—including local variables, synchronized blocks, explicit locks, ThreadLocal, and the modern DateTimeFormatter—along with their advantages and drawbacks.
This article explains why a static SimpleDateFormat instance is not thread‑safe, demonstrates the issue with concurrent parsing, and provides a ThreadLocal‑based solution with complete Java code examples and performance observations.
This article explains how using uppercase YYYY and DD in Java date patterns produces week‑based year and day‑of‑year values, leading to unexpected results around year boundaries, and provides code examples and best‑practice recommendations to avoid these formatting bugs.
This article explains how to use Java's SimpleDateFormat for date‑time formatting and parsing, describes the pattern letters, clarifies the difference between "yyyy" and "YYYY" for week‑year calculations, and shows how ISO 8601 week definitions are supported in Java with practical code examples.
This article explains why Java's SimpleDateFormat is not thread‑safe, demonstrates the resulting concurrency errors, and presents four practical solutions—including per‑call instantiation, ThreadLocal, Apache FastDateFormat, and Java 8's Instant with DateTimeFormatter—along with JMH benchmark results comparing their performance across JDK 8 and JDK 11.
This article narrates a step‑by‑step investigation of a Java server whose heap memory exceeded 95%, detailing log collection, tool usage, thread analysis, and ultimately uncovering a thread‑unsafe SimpleDateFormat that caused an infinite loop and massive memory consumption.
This article explains the legacy java.util.Date class, its limited useful constructors and methods, the more flexible java.util.Calendar API, how to format and parse dates with DateFormat and SimpleDateFormat, and best practices for storing timestamps in databases using long values.