Java : YearMonth (年・月) - API使用例

YearMonth (Java SE 21 & JDK 21) の使い方まとめです。
だいたいのメソッドを網羅済みです。
API仕様書のおともにどうぞ。

概要

ISO-8601暦体系における年月(2007-12など)。

クラス構成

YearMonth は、日付の年と月を表します。
例えば、

2100年8月
1999年1月

などが表現できます。

オブジェクトの生成には of メソッドを使います。

final var yearMonth = YearMonth.of(2100, Month.AUGUST);
System.out.println(yearMonth); // 2100-08

System.out.println(yearMonth.getYear()); // 2100
System.out.println(yearMonth.getMonth()); // AUGUST
System.out.println(yearMonth.getMonthValue()); // 8

メソッド

Temporal adjustInto (Temporal temporal)

指定された時間的オブジェクトをこの年/月になるように調整します。

final var yearMonth = YearMonth.of(1999, Month.DECEMBER);
System.out.println(yearMonth); // 1999-12

final var date = LocalDate.of(2100, 2, 3);
System.out.println(date); // 2100-02-03

final var ret = yearMonth.adjustInto(date);
System.out.println(ret); // 1999-12-03

LocalDate atDay (int dayOfMonth)

この年-月を「月の日」と組み合せてLocalDateを作成します。

final var yearMonth = YearMonth.of(2100, Month.JANUARY);
System.out.println(yearMonth); // 2100-01

System.out.println(yearMonth.atDay(2)); // 2100-01-02
System.out.println(yearMonth.atDay(3)); // 2100-01-03
System.out.println(yearMonth.atDay(31)); // 2100-01-31

try {
    final var ret = yearMonth.atDay(32);
} catch (DateTimeException e) {
    System.out.println("DateTimeException! : " + e.getMessage());
}

// 結果
// ↓
//DateTimeException! : Invalid value for DayOfMonth (valid values 1 - 28/31): 32

LocalDate atEndOfMonth ()

その月の終わりのLocalDateを返します。

final var yearMonth = YearMonth.of(2103, Month.JANUARY);
System.out.println(yearMonth); // 2103-01

System.out.println(yearMonth.atEndOfMonth()); // 2103-01-31
System.out.println(yearMonth.lengthOfMonth()); // 31

final var yearMonth = YearMonth.of(2103, Month.FEBRUARY);
System.out.println(yearMonth); // 2103-02
System.out.println(yearMonth.isLeapYear()); // false

System.out.println(yearMonth.atEndOfMonth()); // 2103-02-28
System.out.println(yearMonth.lengthOfMonth()); // 28

final var yearMonth = YearMonth.of(2104, Month.FEBRUARY);
System.out.println(yearMonth); // 2104-02
System.out.println(yearMonth.isLeapYear()); // true

System.out.println(yearMonth.atEndOfMonth()); // 2104-02-29
System.out.println(yearMonth.lengthOfMonth()); // 29

int compareTo (YearMonth other)

この年-月をもう一方の年-月と比較します。

final var yearMonth1 = YearMonth.of(2100, Month.JANUARY);
final var yearMonth2 = YearMonth.of(2100, Month.JANUARY);

System.out.println(yearMonth1); // 2100-01
System.out.println(yearMonth2); // 2100-01

System.out.println(yearMonth1.compareTo(yearMonth2)); // 0
System.out.println(yearMonth2.compareTo(yearMonth1)); // 0

final var yearMonth1 = YearMonth.of(1999, Month.MAY);
final var yearMonth2 = YearMonth.of(2100, Month.MAY);

System.out.println(yearMonth1); // 1999-05
System.out.println(yearMonth2); // 2100-05

System.out.println(yearMonth1.compareTo(yearMonth2)); // -101
System.out.println(yearMonth2.compareTo(yearMonth1)); // 101

final var yearMonth1 = YearMonth.of(2100, Month.DECEMBER);
final var yearMonth2 = YearMonth.of(2100, Month.APRIL);

System.out.println(yearMonth1); // 2100-12
System.out.println(yearMonth2); // 2100-04

System.out.println(yearMonth1.compareTo(yearMonth2)); // 8
System.out.println(yearMonth2.compareTo(yearMonth1)); // -8

boolean equals (Object obj)

この年-月がもう一方の年-月と等しいかどうかを確認します。

final var yearMonth1 = YearMonth.of(2100, Month.JANUARY);
final var yearMonth2 = YearMonth.of(2100, Month.JANUARY);

System.out.println(yearMonth1); // 2100-01
System.out.println(yearMonth2); // 2100-01

System.out.println(yearMonth1.equals(yearMonth2)); // true
System.out.println(yearMonth2.equals(yearMonth1)); // true

final var yearMonth1 = YearMonth.of(1999, Month.MAY);
final var yearMonth2 = YearMonth.of(2100, Month.MAY);

System.out.println(yearMonth1); // 1999-05
System.out.println(yearMonth2); // 2100-05

System.out.println(yearMonth1.equals(yearMonth2)); // false
System.out.println(yearMonth2.equals(yearMonth1)); // false

final var yearMonth1 = YearMonth.of(2100, Month.DECEMBER);
final var yearMonth2 = YearMonth.of(2100, Month.APRIL);

System.out.println(yearMonth1); // 2100-12
System.out.println(yearMonth2); // 2100-04

System.out.println(yearMonth1.equals(yearMonth2)); // false
System.out.println(yearMonth2.equals(yearMonth1)); // false

String format (DateTimeFormatter formatter)

指定されたフォーマッタを使用してこの年-月を書式設定します。

final var yearMonth = YearMonth.of(2099, Month.JANUARY);
System.out.println(yearMonth); // 2099-01

final var ret1 = yearMonth.format(DateTimeFormatter.ofPattern("yyyy-MM"));
System.out.println(ret1); // 2099-01

final var ret2 = yearMonth.format(DateTimeFormatter.ofPattern("yy-M"));
System.out.println(ret2); // 99-1

static YearMonth from (TemporalAccessor temporal)

時間的オブジェクトからYearMonthのインスタンスを取得します。

final var date = LocalDate.of(2100, 2, 3);
System.out.println(date); // 2100-02-03

final var ret = YearMonth.from(date);
System.out.println(ret); // 2100-02

final var dateTime = LocalDateTime.of(1999, 1, 1, 12, 30);
System.out.println(dateTime); // 1999-01-01T12:30

final var ret = YearMonth.from(dateTime);
System.out.println(ret); // 1999-01

int get (TemporalField field)

この年/月から指定されたフィールドの値をintとして取得します。

final var yearMonth = YearMonth.of(2100, Month.AUGUST);
System.out.println(yearMonth); // 2100-08

System.out.println(yearMonth.get(ChronoField.YEAR)); // 2100
System.out.println(yearMonth.get(ChronoField.MONTH_OF_YEAR)); // 8
System.out.println(yearMonth.get(ChronoField.ERA)); // 1

final var yearMonth = YearMonth.of(-100, Month.DECEMBER);
System.out.println(yearMonth); // -0100-12

System.out.println(yearMonth.get(ChronoField.YEAR)); // -100
System.out.println(yearMonth.get(ChronoField.MONTH_OF_YEAR)); // 12
System.out.println(yearMonth.get(ChronoField.ERA)); // 0

long getLong (TemporalField field)

この年/月から指定されたフィールドの値をlongとして取得します。

final var yearMonth = YearMonth.of(2100, Month.AUGUST);
System.out.println(yearMonth); // 2100-08

System.out.println(yearMonth.getLong(ChronoField.YEAR)); // 2100
System.out.println(yearMonth.getLong(ChronoField.MONTH_OF_YEAR)); // 8
System.out.println(yearMonth.getLong(ChronoField.ERA)); // 1

final var yearMonth = YearMonth.of(-100, Month.DECEMBER);
System.out.println(yearMonth); // -0100-12

System.out.println(yearMonth.getLong(ChronoField.YEAR)); // -100
System.out.println(yearMonth.getLong(ChronoField.MONTH_OF_YEAR)); // 12
System.out.println(yearMonth.getLong(ChronoField.ERA)); // 0

Month getMonth ()

列挙型Monthを使用して、月フィールドを取得します。

final var yearMonth = YearMonth.of(2100, Month.AUGUST);
System.out.println(yearMonth); // 2100-08

System.out.println(yearMonth.getYear()); // 2100
System.out.println(yearMonth.getMonth()); // AUGUST
System.out.println(yearMonth.getMonthValue()); // 8

int getMonthValue ()

月フィールドを取得します(1-12)。

final var yearMonth = YearMonth.of(2100, Month.AUGUST);
System.out.println(yearMonth); // 2100-08

System.out.println(yearMonth.getYear()); // 2100
System.out.println(yearMonth.getMonth()); // AUGUST
System.out.println(yearMonth.getMonthValue()); // 8

int getYear ()

年フィールドを取得します。

final var yearMonth = YearMonth.of(2100, Month.AUGUST);
System.out.println(yearMonth); // 2100-08

System.out.println(yearMonth.getYear()); // 2100
System.out.println(yearMonth.getMonth()); // AUGUST
System.out.println(yearMonth.getMonthValue()); // 8

int hashCode ()

この年-月のハッシュ・コードです。

final var yearMonth = YearMonth.of(2100, Month.JANUARY);
System.out.println(yearMonth); // 2100-01
System.out.println(yearMonth.hashCode()); // 134219828

final var yearMonth = YearMonth.of(-100, Month.AUGUST);
System.out.println(yearMonth); // -0100-08
System.out.println(yearMonth.hashCode()); // -1073741924

boolean isAfter (YearMonth other)

この年/月が、指定された年/月より後にあるかどうかをチェックします。

final var yearMonth = YearMonth.of(2100, Month.JANUARY);
System.out.println(yearMonth); // 2100-01

final var yearMonth2 = YearMonth.of(2099, Month.DECEMBER);
final var yearMonth3 = YearMonth.of(2100, Month.JANUARY);
final var yearMonth4 = YearMonth.of(2100, Month.FEBRUARY);

System.out.println(yearMonth2); // 2099-12
System.out.println(yearMonth3); // 2100-01
System.out.println(yearMonth4); // 2100-02

System.out.println(yearMonth.isAfter(yearMonth2)); // true
System.out.println(yearMonth.isAfter(yearMonth3)); // false
System.out.println(yearMonth.isAfter(yearMonth4)); // false

boolean isBefore (YearMonth other)

この年/月が、指定された年/月より前にあるかどうかをチェックします。

final var yearMonth = YearMonth.of(2100, Month.JANUARY);
System.out.println(yearMonth); // 2100-01

final var yearMonth2 = YearMonth.of(2099, Month.DECEMBER);
final var yearMonth3 = YearMonth.of(2100, Month.JANUARY);
final var yearMonth4 = YearMonth.of(2100, Month.FEBRUARY);

System.out.println(yearMonth2); // 2099-12
System.out.println(yearMonth3); // 2100-01
System.out.println(yearMonth4); // 2100-02

System.out.println(yearMonth.isBefore(yearMonth2)); // false
System.out.println(yearMonth.isBefore(yearMonth3)); // false
System.out.println(yearMonth.isBefore(yearMonth4)); // true

boolean isLeapYear ()

ISO先発暦体系のルールに従って、年がうるう年であるかどうかをチェックします。

final var yearMonth = YearMonth.of(2103, Month.FEBRUARY);
System.out.println(yearMonth); // 2103-02

System.out.println(yearMonth.isLeapYear()); // false
System.out.println(yearMonth.atEndOfMonth()); // 2103-02-28
System.out.println(yearMonth.lengthOfYear()); // 365

final var yearMonth = YearMonth.of(2104, Month.FEBRUARY);
System.out.println(yearMonth); // 2104-02
System.out.println(yearMonth.isLeapYear()); // true
System.out.println(yearMonth.atEndOfMonth()); // 2104-02-29
System.out.println(yearMonth.lengthOfYear()); // 366

boolean isSupported (TemporalField field)

指定されたフィールドがサポートされているかどうかをチェックします。

final var yearMonth = YearMonth.of(2100, Month.JANUARY);
System.out.println(yearMonth); // 2100-01

System.out.println(yearMonth.isSupported(ChronoField.YEAR)); // true
System.out.println(yearMonth.isSupported(ChronoField.YEAR_OF_ERA)); // true
System.out.println(yearMonth.isSupported(ChronoField.ERA)); // true
System.out.println(yearMonth.isSupported(ChronoField.MONTH_OF_YEAR)); // true
System.out.println(yearMonth.isSupported(ChronoField.PROLEPTIC_MONTH)); // true

System.out.println(yearMonth.isSupported(ChronoField.DAY_OF_MONTH)); // false

boolean isSupported (TemporalUnit unit)

指定された単位がサポートされているかどうかをチェックします。

final var yearMonth = YearMonth.of(2100, Month.JANUARY);
System.out.println(yearMonth); // 2100-01

System.out.println(yearMonth.isSupported(ChronoUnit.YEARS)); // true
System.out.println(yearMonth.isSupported(ChronoUnit.MONTHS)); // true
System.out.println(yearMonth.isSupported(ChronoUnit.DECADES)); // true
System.out.println(yearMonth.isSupported(ChronoUnit.CENTURIES)); // true
System.out.println(yearMonth.isSupported(ChronoUnit.MILLENNIA)); // true
System.out.println(yearMonth.isSupported(ChronoUnit.ERAS)); // true

System.out.println(yearMonth.isSupported(ChronoUnit.DAYS)); // false

boolean isValidDay (int dayOfMonth)

「月の日」がこの年-月に対して有効であるかどうかを確認します。

final var yearMonth = YearMonth.of(2100, Month.APRIL);
System.out.println(yearMonth); // 2100-04
System.out.println(yearMonth.atEndOfMonth()); // 2100-04-30

System.out.println(yearMonth.isValidDay(1)); // true
System.out.println(yearMonth.isValidDay(15)); // true
System.out.println(yearMonth.isValidDay(30)); // true
System.out.println(yearMonth.isValidDay(31)); // false

int lengthOfMonth ()

年を考慮に入れて、月の長さを返します。

final var yearMonth = YearMonth.of(2103, Month.JANUARY);
System.out.println(yearMonth); // 2103-01

System.out.println(yearMonth.atEndOfMonth()); // 2103-01-31
System.out.println(yearMonth.lengthOfMonth()); // 31

final var yearMonth = YearMonth.of(2103, Month.FEBRUARY);
System.out.println(yearMonth); // 2103-02
System.out.println(yearMonth.isLeapYear()); // false

System.out.println(yearMonth.atEndOfMonth()); // 2103-02-28
System.out.println(yearMonth.lengthOfMonth()); // 28

final var yearMonth = YearMonth.of(2104, Month.FEBRUARY);
System.out.println(yearMonth); // 2104-02
System.out.println(yearMonth.isLeapYear()); // true

System.out.println(yearMonth.atEndOfMonth()); // 2104-02-29
System.out.println(yearMonth.lengthOfMonth()); // 29

int lengthOfYear ()

年の長さを返します。

final var yearMonth = YearMonth.of(2103, Month.FEBRUARY);
System.out.println(yearMonth); // 2103-02

System.out.println(yearMonth.isLeapYear()); // false
System.out.println(yearMonth.atEndOfMonth()); // 2103-02-28
System.out.println(yearMonth.lengthOfYear()); // 365

final var yearMonth = YearMonth.of(2104, Month.FEBRUARY);
System.out.println(yearMonth); // 2104-02
System.out.println(yearMonth.isLeapYear()); // true
System.out.println(yearMonth.atEndOfMonth()); // 2104-02-29
System.out.println(yearMonth.lengthOfYear()); // 366

YearMonth minus (long amountToSubtract, TemporalUnit unit)

指定された量を減算して、この年/月のコピーを返します。

final var yearMonth = YearMonth.of(2100, Month.FEBRUARY);
System.out.println(yearMonth); // 2100-02

final var ret1 = yearMonth.minus(10, ChronoUnit.YEARS);
System.out.println(ret1); // 2090-02

final var ret2 = yearMonth.minus(20, ChronoUnit.YEARS);
System.out.println(ret2); // 2080-02

final var ret3 = yearMonth.minus(1, ChronoUnit.MONTHS);
System.out.println(ret3); // 2100-01

final var ret4 = yearMonth.minus(2, ChronoUnit.MONTHS);
System.out.println(ret4); // 2099-12

YearMonth minus (TemporalAmount amountToSubtract)

指定された量を減算して、この年/月のコピーを返します。

final var yearMonth = YearMonth.of(2100, Month.FEBRUARY);
System.out.println(yearMonth); // 2100-02

final var ret1 = yearMonth.minus(Period.ofYears(10));
System.out.println(ret1); // 2090-02

final var ret2 = yearMonth.minus(Period.ofYears(20));
System.out.println(ret2); // 2080-02

final var ret3 = yearMonth.minus(Period.ofMonths(1));
System.out.println(ret3); // 2100-01

final var ret4 = yearMonth.minus(Period.ofMonths(2));
System.out.println(ret4); // 2099-12

YearMonth minusMonths (long monthsToSubtract)

指定された月数を減算した、このYearMonthのコピーを返します。

final var yearMonth = YearMonth.of(2100, Month.FEBRUARY);
System.out.println(yearMonth); // 2100-02

final var ret1 = yearMonth.minusMonths(1);
System.out.println(ret1); // 2100-01

final var ret2 = yearMonth.minusMonths(2);
System.out.println(ret2); // 2099-12

YearMonth minusYears (long yearsToSubtract)

指定された年数を減算した、このYearMonthのコピーを返します。

final var yearMonth = YearMonth.of(2100, Month.FEBRUARY);
System.out.println(yearMonth); // 2100-02

final var ret1 = yearMonth.minusYears(10);
System.out.println(ret1); // 2090-02

final var ret2 = yearMonth.minusYears(20);
System.out.println(ret2); // 2080-02

static YearMonth now ()

デフォルトのタイムゾーンのシステム・クロックから現在の年-月を取得します。

final var now = YearMonth.now();
System.out.println(now); // 2024-07

static YearMonth now (Clock clock)

指定されたクロックから現在の年-月を取得します。

// 意図的に1年進めたClock
final var clock = Clock.offset(Clock.systemDefaultZone(), Duration.ofDays(365));

System.out.println(YearMonth.now()); // 2024-07
System.out.println(YearMonth.now(clock)); // 2025-07

static YearMonth now (ZoneId zone)

指定されたタイムゾーンのシステム・クロックから現在の年-月を取得します。

final var zone = ZoneOffset.UTC;
System.out.println(zone); // Z

final var now = YearMonth.now(zone);
System.out.println(now); // 2024-07

static YearMonth of (int year, int month)

年および月からYearMonthのインスタンスを取得します。

final var yearMonth = YearMonth.of(2100, 1);
System.out.println(yearMonth.getYear()); // 2100
System.out.println(yearMonth.getMonth()); // JANUARY
System.out.println(yearMonth.getMonthValue()); // 1

final var yearMonth = YearMonth.of(1999, 11);
System.out.println(yearMonth.getYear()); // 1999
System.out.println(yearMonth.getMonth()); // NOVEMBER
System.out.println(yearMonth.getMonthValue()); // 11

static YearMonth of (int year, Month month)

年および月からYearMonthのインスタンスを取得します。

final var yearMonth = YearMonth.of(2100, Month.JANUARY);
System.out.println(yearMonth.getYear()); // 2100
System.out.println(yearMonth.getMonth()); // JANUARY
System.out.println(yearMonth.getMonthValue()); // 1

final var yearMonth = YearMonth.of(1999, Month.NOVEMBER);
System.out.println(yearMonth.getYear()); // 1999
System.out.println(yearMonth.getMonth()); // NOVEMBER
System.out.println(yearMonth.getMonthValue()); // 11

static YearMonth parse (CharSequence text)

2007-12などのテキスト文字列からYearMonthのインスタンスを取得します。

final var yearMonth1 = YearMonth.parse("2100-01");
System.out.println(yearMonth1); // 2100-01

final var yearMonth2 = YearMonth.parse("1999-12");
System.out.println(yearMonth2); // 1999-12

static YearMonth parse (CharSequence text, DateTimeFormatter formatter)

特定のフォーマッタを使用して、テキスト文字列からYearMonthのインスタンスを取得します。

final var yearMonth1 = YearMonth.parse(
        "2100-01", DateTimeFormatter.ofPattern("yyyy-MM"));
System.out.println(yearMonth1); // 2100-01

final var yearMonth2 = YearMonth.parse(
        "99-5", DateTimeFormatter.ofPattern("yy-M"));
System.out.println(yearMonth2); // 2099-05

YearMonth plus (long amountToAdd, TemporalUnit unit)

指定された量を加算して、この年/月のコピーを返します。

final var yearMonth = YearMonth.of(2100, Month.NOVEMBER);
System.out.println(yearMonth); // 2100-11

final var ret1 = yearMonth.plus(50, ChronoUnit.YEARS);
System.out.println(ret1); // 2150-11

final var ret2 = yearMonth.plus(60, ChronoUnit.YEARS);
System.out.println(ret2); // 2160-11

final var ret3 = yearMonth.plus(1, ChronoUnit.MONTHS);
System.out.println(ret3); // 2100-12

final var ret4 = yearMonth.plus(2, ChronoUnit.MONTHS);
System.out.println(ret4); // 2101-01

YearMonth plus (TemporalAmount amountToAdd)

指定された量を加算して、この年/月のコピーを返します。

final var yearMonth = YearMonth.of(2100, Month.NOVEMBER);
System.out.println(yearMonth); // 2100-11

final var ret1 = yearMonth.plus(Period.ofYears(50));
System.out.println(ret1); // 2150-11

final var ret2 = yearMonth.plus(Period.ofYears(60));
System.out.println(ret2); // 2160-11

final var ret3 = yearMonth.plus(Period.ofMonths(1));
System.out.println(ret3); // 2100-12

final var ret4 = yearMonth.plus(Period.ofMonths(2));
System.out.println(ret4); // 2101-01

YearMonth plusMonths (long monthsToAdd)

指定された月数を加算した、このYearMonthのコピーを返します。

final var yearMonth = YearMonth.of(2100, Month.NOVEMBER);
System.out.println(yearMonth); // 2100-11

final var ret1 = yearMonth.plusMonths(1);
System.out.println(ret1); // 2100-12

final var ret2 = yearMonth.plusMonths(2);
System.out.println(ret2); // 2101-01

YearMonth plusYears (long yearsToAdd)

指定された年数を加算した、このYearMonthのコピーを返します。

final var yearMonth = YearMonth.of(2100, Month.NOVEMBER);
System.out.println(yearMonth); // 2100-11

final var ret1 = yearMonth.plusYears(50);
System.out.println(ret1); // 2150-11

final var ret2 = yearMonth.plusYears(60);
System.out.println(ret2); // 2160-11

<R> R query (TemporalQuery<R> query)

指定された問合せを使用してこの年/月を問い合せます。

final var yearMonth = YearMonth.of(2100, Month.JANUARY);
System.out.println(yearMonth); // 2100-01

final var ret = yearMonth.query(TemporalQueries.precision());
System.out.println(ret); // Months

ValueRange range (TemporalField field)

指定されたフィールドの有効な値の範囲を取得します。

final var yearMonth = YearMonth.of(2100, Month.JANUARY);
System.out.println(yearMonth); // 2100-01

System.out.println(yearMonth.range(ChronoField.YEAR)); // -999999999 - 999999999
System.out.println(yearMonth.range(ChronoField.MONTH_OF_YEAR)); // 1 - 12

String toString ()

この年-月をStringとして出力します(2007-12など)。

final var yearMonth = YearMonth.of(2100, Month.JANUARY);
final var str = yearMonth.toString();
System.out.println(str); // 2100-01

final var yearMonth = YearMonth.of(1999, Month.OCTOBER);
final var str = yearMonth.toString();
System.out.println(str); // 1999-10

long until (Temporal endExclusive, TemporalUnit unit)

別の年/月までの時間量を指定された単位で計算します。

final var start = YearMonth.of(2100, Month.JANUARY);
System.out.println(start); // 2100-01

final var end = YearMonth.of(2150, Month.JANUARY);
System.out.println(end); // 2150-01

final var ret = start.until(end, ChronoUnit.YEARS);
System.out.println(ret); // 50

final var start = YearMonth.of(2100, Month.JANUARY);
System.out.println(start); // 2100-01

final var end = YearMonth.of(2100, Month.AUGUST);
System.out.println(end); // 2100-08

final var ret = start.until(end, ChronoUnit.MONTHS);
System.out.println(ret); // 7

YearMonth with (TemporalAdjuster adjuster)

この年/月の調整済のコピーを返します。

final var yearMonth = YearMonth.of(2100, Month.JANUARY);
System.out.println(yearMonth); // 2100-01

final var ret1 = yearMonth.with(Year.of(1999));
System.out.println(ret1); // 1999-01

final var ret2 = yearMonth.with(Month.AUGUST);
System.out.println(ret2); // 2100-08

YearMonth with (TemporalField field, long newValue)

指定されたフィールドを新しい値に設定して、この年/月のコピーを返します。

final var yearMonth = YearMonth.of(2100, Month.JANUARY);
System.out.println(yearMonth); // 2100-01

final var ret1 = yearMonth.with(ChronoField.YEAR, 1999);
System.out.println(ret1); // 1999-01

final var ret2 = yearMonth.with(ChronoField.MONTH_OF_YEAR, 8);
System.out.println(ret2); // 2100-08

YearMonth withMonth (int month)

月を変更して、このYearMonthのコピーを返します。

final var yearMonth = YearMonth.of(2100, Month.JANUARY);
System.out.println(yearMonth); // 2100-01

final var ret1 = yearMonth.withYear(1999);
System.out.println(ret1); // 1999-01

final var ret2 = yearMonth.withMonth(8);
System.out.println(ret2); // 2100-08

YearMonth withYear (int year)

年を変更して、このYearMonthのコピーを返します。

final var yearMonth = YearMonth.of(2100, Month.JANUARY);
System.out.println(yearMonth); // 2100-01

final var ret1 = yearMonth.withYear(1999);
System.out.println(ret1); // 1999-01

final var ret2 = yearMonth.withMonth(8);
System.out.println(ret2); // 2100-08

API 使用例

Java : YearMonth (年・月) - API使用例

概要

メソッド

Temporal adjustInto (Temporal temporal)

LocalDate atDay (int dayOfMonth)

LocalDate atEndOfMonth ()

int compareTo (YearMonth other)

boolean equals (Object obj)

String format (DateTimeFormatter formatter)

static YearMonth from (TemporalAccessor temporal)

int get (TemporalField field)

long getLong (TemporalField field)

Month getMonth ()

int getMonthValue ()

int getYear ()

int hashCode ()

boolean isAfter (YearMonth other)

boolean isBefore (YearMonth other)

boolean isLeapYear ()

boolean isSupported (TemporalField field)

boolean isSupported (TemporalUnit unit)

boolean isValidDay (int dayOfMonth)

int lengthOfMonth ()

int lengthOfYear ()

YearMonth minus (long amountToSubtract, TemporalUnit unit)

YearMonth minus (TemporalAmount amountToSubtract)

YearMonth minusMonths (long monthsToSubtract)

YearMonth minusYears (long yearsToSubtract)

static YearMonth now ()

static YearMonth now (Clock clock)

static YearMonth now (ZoneId zone)

static YearMonth of (int year, int month)

static YearMonth of (int year, Month month)

static YearMonth parse (CharSequence text)

static YearMonth parse (CharSequence text, DateTimeFormatter formatter)

YearMonth plus (long amountToAdd, TemporalUnit unit)

YearMonth plus (TemporalAmount amountToAdd)

YearMonth plusMonths (long monthsToAdd)

YearMonth plusYears (long yearsToAdd)

<R> R query (TemporalQuery<R> query)

ValueRange range (TemporalField field)

String toString ()

long until (Temporal endExclusive, TemporalUnit unit)

YearMonth with (TemporalAdjuster adjuster)

YearMonth with (TemporalField field, long newValue)

YearMonth withMonth (int month)

YearMonth withYear (int year)

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