findbugs | STCAL_INVOKE_ON_STATIC_DATE_FORMAT_INSTANCE

Call to static DateFormat As the JavaDoc states, DateFormats are inherently unsafe for multithreaded use. The detector has found a call to an instance of DateFormat that has been obtained via a static field. This looks suspicous

STCAL_INVOKE_ON_STATIC_DATE_FORMAT_INSTANCE

bug 报错示例：

    private static final SimpleDateFormat SIMPLE_DATE_FORMAT = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");

    private static String demo() {
        return SIMPLE_DATE_FORMAT.format(new Date());

    }

bug原因：

对于多线程使用，dateformat本质上是不安全的。检测器发现了对DateFormat实例的调用，该调用是通过静态字段获得的。

修复方法：

private static final String SIMPLE_DATE_FORMAT = "yyyy-yyyy/MM/dd HH:mm:ss-dd";

    private static String demo() {
        return new SimpleDateFormat(SIMPLE_DATE_FORMAT).format(new Date());

    }

每次重新生成新的SimpleDateFormat对象，问题解决