*** 설명 ***
기존 SimpleDateFormat 보다 빠름.
Thread Safe.
Apache Commons Lang 라이브러리 필요.
*** 사용예 ***
FastDateFormat fdf = FastDateFormat.getInstance("yyyyMMdd");
System.out.println("FastDateFormat =" + fdf.format(Calendar.getInstance()));
*** maven repository ***
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-lang3</artifactId>
<version>3.4</version>
</dependency>
