| [`DateFormat`][] is not thread-safe. The documentation recommends creating |
| separate format instances for each thread. If multiple threads access a format |
| concurrently, it must be synchronized externally. |
| |
| The [Google Java Style Guide ยง5.2.4][style] requires `CONSTANT_CASE` to only be |
| used for static final fields whose contents are deeply immutable and whose |
| methods have no detectable side effects, so fields of type `DateFormat` should |
| not use `CONSTANT_CASE`. |
| |
| TIP: Consider using the `java.time` API added in Java8, in particular |
| [`DateTimeFormatter`][]. One its many advantages over `DateFormat` is that it is |
| immutable and thread-safe. |
| |
| If the date formatter is accessed by multiple threads, consider using |
| [`ThreadLocal`][]: |
| |
| ```java |
| private static final ThreadLocal<DateFormat> DATE_FORMAT = |
| ThreadLocal.withInitial(() -> new SimpleDateFormat("yyyy-MM-dd HH:mm")); |
| |
| ``` |
| |
| If the field is never accessed by multiple threads, rename it to use |
| `lowerCamelCase`. |
| |
| ```java |
| // not thread safe |
| private static final DateFormat dateFormat = |
| new SimpleDateFormat("yyyy-MM-dd HH:mm"); |
| |
| ``` |
| |
| [`DateFormat`]: http://docs.oracle.com/javase/8/docs/api/java/text/DateFormat.html |
| [`ThreadLocal`]: http://docs.oracle.com/javase/8/docs/api/java/lang/ThreadLocal.html |
| [`DateTimeFormatter`]: https://docs.oracle.com/javase/8/docs/api/java/time/format/DateTimeFormatter.html |
| |
| [style]: https://google.github.io/styleguide/javaguide.html#s5.2.4-constant-names |
