Java로 날짜 및 시간 처리

java.time.LocalDateTime(java8)

DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyy/MM/dd HH ss");

(java7이면) 조다타임.

java.util.Date(최대한 사용하지 않음)

SimpleDateFormat sdf = new SimpleDateFormat("kk:mm");
// 11:30以前の場合
if (sdf.parse(data.get(1)).compareTo(sdf.parse("11:30")) <= 0) {
　　System.out.println("お昼前だよ");
}

            public static java.sql.Date toSqlDate(java.util.Date date) {
                return new java.sql.Date(date.getTime());
            }

java.util.Calendar(가급적 사용하지 않음)

SimpleDateFormat sdf = new SimpleDateFormat("yyyy/MM/dd HH ss");

처리 시간

org.apache.commons

compile group: 'org.apache.commons', name: 'commons-lang3', version: '3.10'

StopWatch stopWatch = new StopWatch();

// 計測開始
stopWatch.start();

Thread.sleep(500);

// 計測停止
stopWatch.stop();

// 経過時間出力
System.out.println(stopWatch.getTime()); // ⇒500

org.springframework.util.StopWatch

StopWatch stopWatch = new StopWatch();
stopWatch.start();
// ... more
stopWatch.stop();
System.out.println(stopWatch.getTotalTimeMillis());
System.out.println(stopWatch.prettyPrint());

평면

    // 全体の「時間:分:秒」
     private String formatedTimeV2(long millis) {
            return String.format("%02d:%02d:%02d", 
                    TimeUnit.MILLISECONDS.toHours(millis),
                    TimeUnit.MILLISECONDS.toMinutes(millis) - 
                    TimeUnit.HOURS.toMinutes(TimeUnit.MILLISECONDS.toHours(millis)),
                    TimeUnit.MILLISECONDS.toSeconds(millis) - 
                    TimeUnit.MINUTES.toSeconds(TimeUnit.MILLISECONDS.toMinutes(millis))
             );
     }
    // 個別の「分 min, 秒 sec」
    private String formatedTime(long millis) {
        return String.format("%d min, %d sec", 
                TimeUnit.MILLISECONDS.toMinutes(millis),
                TimeUnit.MILLISECONDS.toSeconds(millis) - 
                TimeUnit.MINUTES.toSeconds(TimeUnit.MILLISECONDS.toMinutes(millis))
            );
    }

    @Test
    public void formatTime() throws InterruptedException {
        long start = System.currentTimeMillis();
        Thread.sleep(1000);
        long end = System.currentTimeMillis();
        System.out.println(formatedTime(end - start));
    }

0 min, 1 sec