LocalDate(Java 8)の基本

初めに

日付だけの処理をするケースは結構ある。
Java8より前のCalendear,Dateは時間も含まれるので、できればJava8から導入されたLocalDateで実装したい。
そのため、LocalDateの基本的な使用方法を実践してみた。

ソースは以下にある。
https://github.com/xaatw0/quiita/blob/master/src/LocalDateTest.java

サンプル

LocalDateTest.java

@Test
public void now(){
    // 2015/07/27に実施
    LocalDate date = LocalDate.now();
    assertThat(date.getYear(), is(2015));
    assertThat(date.getMonth(), is(Month.JULY));
    assertThat(date.getDayOfMonth(), is(27));
}


@Test
public void of1(){
    LocalDate date = LocalDate.of(2015, 10, 1);
    assertThat(date.getYear(), is(2015));
    assertThat(date.getMonth(), is(Month.OCTOBER));
    assertThat(date.getMonthValue(), is(10));
    assertThat(date.getDayOfMonth(), is(1));

    assertThat(date.getDayOfYear(), is(274));
    assertThat(date.getDayOfMonth(), is(1));
    //assertThat(date.getDayOfWeek(), is(4)); // この書き方ではテスト失敗(コンパイルは通る)
    assertThat(date.getDayOfWeek(), is(DayOfWeek.THURSDAY));
}

@Test
public void of2(){
    LocalDate date = LocalDate.of(2015, Month.OCTOBER, 1);
    assertThat(date.getYear(), is(2015));
    assertThat(date.getMonth(), is(Month.OCTOBER));
    assertThat(date.getMonthValue(), is(10));
    assertThat(date.getDayOfMonth(), is(1));
}

@Test
public void plus(){
    LocalDate date = LocalDate.of(2015, Month.OCTOBER, 1);
    assertThat(date.getYear(), is(2015));
    assertThat(date.getMonth(), is(Month.OCTOBER));
    assertThat(date.getDayOfMonth(), is(1));

    LocalDate date2 = date.plusDays(3);
    assertThat(date2.getYear(), is(2015));
    assertThat(date2.getMonth(), is(Month.OCTOBER));
    assertThat(date2.getDayOfMonth(), is(4));

    LocalDate date3 = date.plusMonths(3);
    assertThat(date3.getYear(), is(2016));
    assertThat(date3.getMonth(), is(Month.JANUARY));
    assertThat(date3.getDayOfMonth(), is(1));

    LocalDate date4 = date.plusYears(5);
    assertThat(date4.getYear(), is(2020));
    assertThat(date4.getMonth(), is(Month.OCTOBER));
    assertThat(date4.getDayOfMonth(), is(1));

    // 変化していないことを確認
    assertThat(date.getYear(), is(2015));
    assertThat(date.getMonth(), is(Month.OCTOBER));
    assertThat(date.getDayOfMonth(), is(1));
}

@Test
public void minus(){
    LocalDate date = LocalDate.of(2015, Month.OCTOBER, 1);
    assertThat(date.getYear(), is(2015));
    assertThat(date.getMonth(), is(Month.OCTOBER));
    assertThat(date.getDayOfMonth(), is(1));

    LocalDate date2 = date.minusDays(3);
    assertThat(date2.getYear(), is(2015));
    assertThat(date2.getMonth(), is(Month.SEPTEMBER));
    assertThat(date2.getDayOfMonth(), is(28));

    LocalDate date3 = date.minusMonths(3);
    assertThat(date3.getYear(), is(2015));
    assertThat(date3.getMonth(), is(Month.JULY));
    assertThat(date3.getDayOfMonth(), is(1));

    LocalDate date4 = date.minusYears(5);
    assertThat(date4.getYear(), is(2010));
    assertThat(date4.getMonth(), is(Month.OCTOBER));
    assertThat(date4.getDayOfMonth(), is(1));

    // 変化していないことを確認
    assertThat(date.getYear(), is(2015));
    assertThat(date.getMonth(), is(Month.OCTOBER));
    assertThat(date.getDayOfMonth(), is(1));
}

@Test
public void Period(){
    LocalDate start = LocalDate.of(2015, Month.OCTOBER, 1);
    LocalDate end = LocalDate.of(2016, Month.OCTOBER, 1);

    Period period = Period.between(start, end);
    assertThat(period.getYears(),is(1));
    assertThat(period.getMonths(),is(0));
    assertThat(period.getDays(),is(0));

    assertThat(period.toTotalMonths(),is(12L));

    period = Period.between(
            LocalDate.of(2011, Month.JANUARY, 1),
            LocalDate.of(2012, Month.FEBRUARY, 2));

    assertThat(period.getYears(),is(1));
    assertThat(period.getMonths(),is(1));
    assertThat(period.getDays(),is(1));

    // 開始日の方が未来日の場合、値はマイナスになる
    period = Period.between(
            LocalDate.of(2012, Month.FEBRUARY, 2),
            LocalDate.of(2011, Month.JANUARY, 1));

    assertThat(period.getYears(),is(-1));
    assertThat(period.getMonths(),is(-1));
    assertThat(period.getDays(),is(-1));
}

@Test
public void parse(){
    LocalDate date = LocalDate.of(2015, 8, 18);
    assertThat(LocalDate.parse("2015-08-18"), is(date));
    assertThat(LocalDate.parse("2015-08-18", DateTimeFormatter.ISO_DATE), is(date));
    assertThat(LocalDate.parse("2015-08-18", DateTimeFormatter.ISO_LOCAL_DATE), is(date));

    assertThat(LocalDate.parse("20150818", DateTimeFormatter.BASIC_ISO_DATE), is(date));
}

@Test
public void format(){

    // 2015年8月18日 230日目、34週の火曜日
    LocalDate date = LocalDate.of(2015, 8, 18);
    assertThat(date.format(DateTimeFormatter.ISO_DATE), is("2015-08-18"));
    assertThat(date.format(DateTimeFormatter.ISO_LOCAL_DATE), is("2015-08-18"));
    assertThat(date.format(DateTimeFormatter.BASIC_ISO_DATE), is("20150818"));
    assertThat(date.format(DateTimeFormatter.ISO_ORDINAL_DATE), is("2015-230"));
    assertThat(date.format(DateTimeFormatter.ISO_WEEK_DATE), is("2015-W34-2"));
}

@Test
public void DateTimeFormatter(){

    // 出力する日付のフォーマットを変更する
    DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy/MM/dd");

    LocalDate date = LocalDate.of(2015, 8, 18);
    assertThat(date.format(formatter), is("2015/08/18"));
}