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 * Copyright (c) 2012-2013, Stephen Colebourne & Michael Nascimento Santos
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package java.time.temporal;

import static java.time.temporal.ChronoField.DAY_OF_MONTH;
import static java.time.temporal.ChronoField.DAY_OF_WEEK;
import static java.time.temporal.ChronoField.DAY_OF_YEAR;
import static java.time.temporal.ChronoUnit.DAYS;
import static java.time.temporal.ChronoUnit.MONTHS;
import static java.time.temporal.ChronoUnit.YEARS;

import java.time.DayOfWeek;
import java.time.LocalDate;
import java.util.Objects;
import java.util.function.UnaryOperator;


Common and useful TemporalAdjusters.


Adjusters are a key tool for modifying temporal objects.
They exist to externalize the process of adjustment, permitting different
approaches, as per the strategy design pattern.
Examples might be an adjuster that sets the date avoiding weekends, or one that
sets the date to the last day of the month.

 There are two equivalent ways of using a TemporalAdjuster. The first is to invoke the method on the interface directly. The second is to use Temporal.with(TemporalAdjuster): 
  // these two lines are equivalent, but the second approach is recommended
  temporal = thisAdjuster.adjustInto(temporal);
  temporal = temporal.with(thisAdjuster);

 It is recommended to use the second approach, with(TemporalAdjuster), as it is a lot clearer to read in code. 

This class contains a standard set of adjusters, available as static methods.
These include:

    

  • finding the first or last day of the month

  • finding the first day of next month

  • finding the first or last day of the year

  • finding the first day of next year

  • finding the first or last day-of-week within a month, such as "first Wednesday in June"

  • finding the next or previous day-of-week, such as "next Thursday"



See Also:
Implementation Requirements:
All the implementations supplied by the static methods are immutable.
Since:1.8
/**
 * Common and useful TemporalAdjusters.
 * <p>
 * Adjusters are a key tool for modifying temporal objects.
 * They exist to externalize the process of adjustment, permitting different
 * approaches, as per the strategy design pattern.
 * Examples might be an adjuster that sets the date avoiding weekends, or one that
 * sets the date to the last day of the month.
 * <p>
 * There are two equivalent ways of using a {@code TemporalAdjuster}.
 * The first is to invoke the method on the interface directly.
 * The second is to use {@link Temporal#with(TemporalAdjuster)}:
 * <pre>
 *   // these two lines are equivalent, but the second approach is recommended
 *   temporal = thisAdjuster.adjustInto(temporal);
 *   temporal = temporal.with(thisAdjuster);
 * </pre>
 * It is recommended to use the second approach, {@code with(TemporalAdjuster)},
 * as it is a lot clearer to read in code.
 * <p>
 * This class contains a standard set of adjusters, available as static methods.
 * These include:
 * <ul>
 * <li>finding the first or last day of the month
 * <li>finding the first day of next month
 * <li>finding the first or last day of the year
 * <li>finding the first day of next year
 * <li>finding the first or last day-of-week within a month, such as "first Wednesday in June"
 * <li>finding the next or previous day-of-week, such as "next Thursday"
 * </ul>
 *
 * @implSpec
 * All the implementations supplied by the static methods are immutable.
 *
 * @see TemporalAdjuster
 * @since 1.8
 */
public final class TemporalAdjusters {

    
Private constructor since this is a utility class.

/**
     * Private constructor since this is a utility class.
     */
    private TemporalAdjusters() {
    }

    //-----------------------------------------------------------------------
    
Obtains a TemporalAdjuster that wraps a date adjuster. 
 The TemporalAdjuster is based on the low level Temporal interface. This method allows an adjustment from LocalDate to LocalDate to be wrapped to match the temporal-based interface. This is provided for convenience to make user-written adjusters simpler. 

In general, user-written adjusters should be static constants:


 static TemporalAdjuster TWO_DAYS_LATER =
      TemporalAdjusters.ofDateAdjuster(date -> date.plusDays(2));



Params:
  • dateBasedAdjuster –  the date-based adjuster, not null
Returns:the temporal adjuster wrapping on the date adjuster, not null
/**
     * Obtains a {@code TemporalAdjuster} that wraps a date adjuster.
     * <p>
     * The {@code TemporalAdjuster} is based on the low level {@code Temporal} interface.
     * This method allows an adjustment from {@code LocalDate} to {@code LocalDate}
     * to be wrapped to match the temporal-based interface.
     * This is provided for convenience to make user-written adjusters simpler.
     * <p>
     * In general, user-written adjusters should be static constants:
     * <pre>{@code
     *  static TemporalAdjuster TWO_DAYS_LATER =
     *       TemporalAdjusters.ofDateAdjuster(date -> date.plusDays(2));
     * }</pre>
     *
     * @param dateBasedAdjuster  the date-based adjuster, not null
     * @return the temporal adjuster wrapping on the date adjuster, not null
     */
    public static TemporalAdjuster ofDateAdjuster(UnaryOperator<LocalDate> dateBasedAdjuster) {
        Objects.requireNonNull(dateBasedAdjuster, "dateBasedAdjuster");
        return (temporal) -> {
            LocalDate input = LocalDate.from(temporal);
            LocalDate output = dateBasedAdjuster.apply(input);
            return temporal.with(output);
        };
    }

    //-----------------------------------------------------------------------
    
Returns the "first day of month" adjuster, which returns a new date set to
the first day of the current month.


The ISO calendar system behaves as follows:

The input 2011-01-15 will return 2011-01-01.

The input 2011-02-15 will return 2011-02-01.


The behavior is suitable for use with most calendar systems.
It is equivalent to:

 temporal.with(DAY_OF_MONTH, 1);



Returns:the first day-of-month adjuster, not null
/**
     * Returns the "first day of month" adjuster, which returns a new date set to
     * the first day of the current month.
     * <p>
     * The ISO calendar system behaves as follows:<br>
     * The input 2011-01-15 will return 2011-01-01.<br>
     * The input 2011-02-15 will return 2011-02-01.
     * <p>
     * The behavior is suitable for use with most calendar systems.
     * It is equivalent to:
     * <pre>
     *  temporal.with(DAY_OF_MONTH, 1);
     * </pre>
     *
     * @return the first day-of-month adjuster, not null
     */
    public static TemporalAdjuster firstDayOfMonth() {
        return (temporal) -> temporal.with(DAY_OF_MONTH, 1);
    }

    
Returns the "last day of month" adjuster, which returns a new date set to
the last day of the current month.


The ISO calendar system behaves as follows:

The input 2011-01-15 will return 2011-01-31.

The input 2011-02-15 will return 2011-02-28.

The input 2012-02-15 will return 2012-02-29 (leap year).

The input 2011-04-15 will return 2011-04-30.


The behavior is suitable for use with most calendar systems.
It is equivalent to:

 long lastDay = temporal.range(DAY_OF_MONTH).getMaximum();
 temporal.with(DAY_OF_MONTH, lastDay);



Returns:the last day-of-month adjuster, not null
/**
     * Returns the "last day of month" adjuster, which returns a new date set to
     * the last day of the current month.
     * <p>
     * The ISO calendar system behaves as follows:<br>
     * The input 2011-01-15 will return 2011-01-31.<br>
     * The input 2011-02-15 will return 2011-02-28.<br>
     * The input 2012-02-15 will return 2012-02-29 (leap year).<br>
     * The input 2011-04-15 will return 2011-04-30.
     * <p>
     * The behavior is suitable for use with most calendar systems.
     * It is equivalent to:
     * <pre>
     *  long lastDay = temporal.range(DAY_OF_MONTH).getMaximum();
     *  temporal.with(DAY_OF_MONTH, lastDay);
     * </pre>
     *
     * @return the last day-of-month adjuster, not null
     */
    public static TemporalAdjuster lastDayOfMonth() {
        return (temporal) -> temporal.with(DAY_OF_MONTH, temporal.range(DAY_OF_MONTH).getMaximum());
    }

    
Returns the "first day of next month" adjuster, which returns a new date set to
the first day of the next month.


The ISO calendar system behaves as follows:

The input 2011-01-15 will return 2011-02-01.

The input 2011-02-15 will return 2011-03-01.


The behavior is suitable for use with most calendar systems.
It is equivalent to:

 temporal.with(DAY_OF_MONTH, 1).plus(1, MONTHS);



Returns:the first day of next month adjuster, not null
/**
     * Returns the "first day of next month" adjuster, which returns a new date set to
     * the first day of the next month.
     * <p>
     * The ISO calendar system behaves as follows:<br>
     * The input 2011-01-15 will return 2011-02-01.<br>
     * The input 2011-02-15 will return 2011-03-01.
     * <p>
     * The behavior is suitable for use with most calendar systems.
     * It is equivalent to:
     * <pre>
     *  temporal.with(DAY_OF_MONTH, 1).plus(1, MONTHS);
     * </pre>
     *
     * @return the first day of next month adjuster, not null
     */
    public static TemporalAdjuster firstDayOfNextMonth() {
        return (temporal) -> temporal.with(DAY_OF_MONTH, 1).plus(1, MONTHS);
    }

    //-----------------------------------------------------------------------
    
Returns the "first day of year" adjuster, which returns a new date set to
the first day of the current year.


The ISO calendar system behaves as follows:

The input 2011-01-15 will return 2011-01-01.

The input 2011-02-15 will return 2011-01-01.



The behavior is suitable for use with most calendar systems.
It is equivalent to:

 temporal.with(DAY_OF_YEAR, 1);



Returns:the first day-of-year adjuster, not null
/**
     * Returns the "first day of year" adjuster, which returns a new date set to
     * the first day of the current year.
     * <p>
     * The ISO calendar system behaves as follows:<br>
     * The input 2011-01-15 will return 2011-01-01.<br>
     * The input 2011-02-15 will return 2011-01-01.<br>
     * <p>
     * The behavior is suitable for use with most calendar systems.
     * It is equivalent to:
     * <pre>
     *  temporal.with(DAY_OF_YEAR, 1);
     * </pre>
     *
     * @return the first day-of-year adjuster, not null
     */
    public static TemporalAdjuster firstDayOfYear() {
        return (temporal) -> temporal.with(DAY_OF_YEAR, 1);
    }

    
Returns the "last day of year" adjuster, which returns a new date set to
the last day of the current year.


The ISO calendar system behaves as follows:

The input 2011-01-15 will return 2011-12-31.

The input 2011-02-15 will return 2011-12-31.



The behavior is suitable for use with most calendar systems.
It is equivalent to:

 long lastDay = temporal.range(DAY_OF_YEAR).getMaximum();
 temporal.with(DAY_OF_YEAR, lastDay);



Returns:the last day-of-year adjuster, not null
/**
     * Returns the "last day of year" adjuster, which returns a new date set to
     * the last day of the current year.
     * <p>
     * The ISO calendar system behaves as follows:<br>
     * The input 2011-01-15 will return 2011-12-31.<br>
     * The input 2011-02-15 will return 2011-12-31.<br>
     * <p>
     * The behavior is suitable for use with most calendar systems.
     * It is equivalent to:
     * <pre>
     *  long lastDay = temporal.range(DAY_OF_YEAR).getMaximum();
     *  temporal.with(DAY_OF_YEAR, lastDay);
     * </pre>
     *
     * @return the last day-of-year adjuster, not null
     */
    public static TemporalAdjuster lastDayOfYear() {
        return (temporal) -> temporal.with(DAY_OF_YEAR, temporal.range(DAY_OF_YEAR).getMaximum());
    }

    
Returns the "first day of next year" adjuster, which returns a new date set to
the first day of the next year.


The ISO calendar system behaves as follows:

The input 2011-01-15 will return 2012-01-01.


The behavior is suitable for use with most calendar systems.
It is equivalent to:

 temporal.with(DAY_OF_YEAR, 1).plus(1, YEARS);



Returns:the first day of next month adjuster, not null
/**
     * Returns the "first day of next year" adjuster, which returns a new date set to
     * the first day of the next year.
     * <p>
     * The ISO calendar system behaves as follows:<br>
     * The input 2011-01-15 will return 2012-01-01.
     * <p>
     * The behavior is suitable for use with most calendar systems.
     * It is equivalent to:
     * <pre>
     *  temporal.with(DAY_OF_YEAR, 1).plus(1, YEARS);
     * </pre>
     *
     * @return the first day of next month adjuster, not null
     */
    public static TemporalAdjuster firstDayOfNextYear() {
        return (temporal) -> temporal.with(DAY_OF_YEAR, 1).plus(1, YEARS);
    }

    //-----------------------------------------------------------------------
    
Returns the first in month adjuster, which returns a new date
in the same month with the first matching day-of-week.
This is used for expressions like 'first Tuesday in March'.


The ISO calendar system behaves as follows:

The input 2011-12-15 for (MONDAY) will return 2011-12-05.

The input 2011-12-15 for (FRIDAY) will return 2011-12-02.


 The behavior is suitable for use with most calendar systems. It uses the DAY_OF_WEEK and DAY_OF_MONTH fields and the DAYS unit, and assumes a seven day week. 
Params:
  • dayOfWeek –  the day-of-week, not null
Returns:the first in month adjuster, not null
/**
     * Returns the first in month adjuster, which returns a new date
     * in the same month with the first matching day-of-week.
     * This is used for expressions like 'first Tuesday in March'.
     * <p>
     * The ISO calendar system behaves as follows:<br>
     * The input 2011-12-15 for (MONDAY) will return 2011-12-05.<br>
     * The input 2011-12-15 for (FRIDAY) will return 2011-12-02.<br>
     * <p>
     * The behavior is suitable for use with most calendar systems.
     * It uses the {@code DAY_OF_WEEK} and {@code DAY_OF_MONTH} fields
     * and the {@code DAYS} unit, and assumes a seven day week.
     *
     * @param dayOfWeek  the day-of-week, not null
     * @return the first in month adjuster, not null
     */
    public static TemporalAdjuster firstInMonth(DayOfWeek dayOfWeek) {
        return TemporalAdjusters.dayOfWeekInMonth(1, dayOfWeek);
    }

    
Returns the last in month adjuster, which returns a new date
in the same month with the last matching day-of-week.
This is used for expressions like 'last Tuesday in March'.


The ISO calendar system behaves as follows:

The input 2011-12-15 for (MONDAY) will return 2011-12-26.

The input 2011-12-15 for (FRIDAY) will return 2011-12-30.


 The behavior is suitable for use with most calendar systems. It uses the DAY_OF_WEEK and DAY_OF_MONTH fields and the DAYS unit, and assumes a seven day week. 
Params:
  • dayOfWeek –  the day-of-week, not null
Returns:the first in month adjuster, not null
/**
     * Returns the last in month adjuster, which returns a new date
     * in the same month with the last matching day-of-week.
     * This is used for expressions like 'last Tuesday in March'.
     * <p>
     * The ISO calendar system behaves as follows:<br>
     * The input 2011-12-15 for (MONDAY) will return 2011-12-26.<br>
     * The input 2011-12-15 for (FRIDAY) will return 2011-12-30.<br>
     * <p>
     * The behavior is suitable for use with most calendar systems.
     * It uses the {@code DAY_OF_WEEK} and {@code DAY_OF_MONTH} fields
     * and the {@code DAYS} unit, and assumes a seven day week.
     *
     * @param dayOfWeek  the day-of-week, not null
     * @return the first in month adjuster, not null
     */
    public static TemporalAdjuster lastInMonth(DayOfWeek dayOfWeek) {
        return TemporalAdjusters.dayOfWeekInMonth(-1, dayOfWeek);
    }

    
Returns the day-of-week in month adjuster, which returns a new date
with the ordinal day-of-week based on the month.
This is used for expressions like the 'second Tuesday in March'.


The ISO calendar system behaves as follows:

The input 2011-12-15 for (1,TUESDAY) will return 2011-12-06.

The input 2011-12-15 for (2,TUESDAY) will return 2011-12-13.

The input 2011-12-15 for (3,TUESDAY) will return 2011-12-20.

The input 2011-12-15 for (4,TUESDAY) will return 2011-12-27.

The input 2011-12-15 for (5,TUESDAY) will return 2012-01-03.

The input 2011-12-15 for (-1,TUESDAY) will return 2011-12-27 (last in month).

The input 2011-12-15 for (-4,TUESDAY) will return 2011-12-06 (3 weeks before last in month).

The input 2011-12-15 for (-5,TUESDAY) will return 2011-11-29 (4 weeks before last in month).

The input 2011-12-15 for (0,TUESDAY) will return 2011-11-29 (last in previous month).



For a positive or zero ordinal, the algorithm is equivalent to finding the first
day-of-week that matches within the month and then adding a number of weeks to it.
For a negative ordinal, the algorithm is equivalent to finding the last
day-of-week that matches within the month and then subtracting a number of weeks to it.
The ordinal number of weeks is not validated and is interpreted leniently
according to this algorithm. This definition means that an ordinal of zero finds
the last matching day-of-week in the previous month.

 The behavior is suitable for use with most calendar systems. It uses the DAY_OF_WEEK and DAY_OF_MONTH fields and the DAYS unit, and assumes a seven day week. 
Params:
  • ordinal –  the week within the month, unbounded but typically from -5 to 5
  • dayOfWeek –  the day-of-week, not null
Returns:the day-of-week in month adjuster, not null
/**
     * Returns the day-of-week in month adjuster, which returns a new date
     * with the ordinal day-of-week based on the month.
     * This is used for expressions like the 'second Tuesday in March'.
     * <p>
     * The ISO calendar system behaves as follows:<br>
     * The input 2011-12-15 for (1,TUESDAY) will return 2011-12-06.<br>
     * The input 2011-12-15 for (2,TUESDAY) will return 2011-12-13.<br>
     * The input 2011-12-15 for (3,TUESDAY) will return 2011-12-20.<br>
     * The input 2011-12-15 for (4,TUESDAY) will return 2011-12-27.<br>
     * The input 2011-12-15 for (5,TUESDAY) will return 2012-01-03.<br>
     * The input 2011-12-15 for (-1,TUESDAY) will return 2011-12-27 (last in month).<br>
     * The input 2011-12-15 for (-4,TUESDAY) will return 2011-12-06 (3 weeks before last in month).<br>
     * The input 2011-12-15 for (-5,TUESDAY) will return 2011-11-29 (4 weeks before last in month).<br>
     * The input 2011-12-15 for (0,TUESDAY) will return 2011-11-29 (last in previous month).<br>
     * <p>
     * For a positive or zero ordinal, the algorithm is equivalent to finding the first
     * day-of-week that matches within the month and then adding a number of weeks to it.
     * For a negative ordinal, the algorithm is equivalent to finding the last
     * day-of-week that matches within the month and then subtracting a number of weeks to it.
     * The ordinal number of weeks is not validated and is interpreted leniently
     * according to this algorithm. This definition means that an ordinal of zero finds
     * the last matching day-of-week in the previous month.
     * <p>
     * The behavior is suitable for use with most calendar systems.
     * It uses the {@code DAY_OF_WEEK} and {@code DAY_OF_MONTH} fields
     * and the {@code DAYS} unit, and assumes a seven day week.
     *
     * @param ordinal  the week within the month, unbounded but typically from -5 to 5
     * @param dayOfWeek  the day-of-week, not null
     * @return the day-of-week in month adjuster, not null
     */
    public static TemporalAdjuster dayOfWeekInMonth(int ordinal, DayOfWeek dayOfWeek) {
        Objects.requireNonNull(dayOfWeek, "dayOfWeek");
        int dowValue = dayOfWeek.getValue();
        if (ordinal >= 0) {
            return (temporal) -> {
                Temporal temp = temporal.with(DAY_OF_MONTH, 1);
                int curDow = temp.get(DAY_OF_WEEK);
                int dowDiff = (dowValue - curDow + 7) % 7;
                dowDiff += (ordinal - 1L) * 7L;  // safe from overflow
                return temp.plus(dowDiff, DAYS);
            };
        } else {
            return (temporal) -> {
                Temporal temp = temporal.with(DAY_OF_MONTH, temporal.range(DAY_OF_MONTH).getMaximum());
                int curDow = temp.get(DAY_OF_WEEK);
                int daysDiff = dowValue - curDow;
                daysDiff = (daysDiff == 0 ? 0 : (daysDiff > 0 ? daysDiff - 7 : daysDiff));
                daysDiff -= (-ordinal - 1L) * 7L;  // safe from overflow
                return temp.plus(daysDiff, DAYS);
            };
        }
    }

    //-----------------------------------------------------------------------
    
Returns the next day-of-week adjuster, which adjusts the date to the
first occurrence of the specified day-of-week after the date being adjusted.


The ISO calendar system behaves as follows:

The input 2011-01-15 (a Saturday) for parameter (MONDAY) will return 2011-01-17 (two days later).

The input 2011-01-15 (a Saturday) for parameter (WEDNESDAY) will return 2011-01-19 (four days later).

The input 2011-01-15 (a Saturday) for parameter (SATURDAY) will return 2011-01-22 (seven days later).

 The behavior is suitable for use with most calendar systems. It uses the DAY_OF_WEEK field and the DAYS unit, and assumes a seven day week. 
Params:
  • dayOfWeek –  the day-of-week to move the date to, not null
Returns:the next day-of-week adjuster, not null
/**
     * Returns the next day-of-week adjuster, which adjusts the date to the
     * first occurrence of the specified day-of-week after the date being adjusted.
     * <p>
     * The ISO calendar system behaves as follows:<br>
     * The input 2011-01-15 (a Saturday) for parameter (MONDAY) will return 2011-01-17 (two days later).<br>
     * The input 2011-01-15 (a Saturday) for parameter (WEDNESDAY) will return 2011-01-19 (four days later).<br>
     * The input 2011-01-15 (a Saturday) for parameter (SATURDAY) will return 2011-01-22 (seven days later).
     * <p>
     * The behavior is suitable for use with most calendar systems.
     * It uses the {@code DAY_OF_WEEK} field and the {@code DAYS} unit,
     * and assumes a seven day week.
     *
     * @param dayOfWeek  the day-of-week to move the date to, not null
     * @return the next day-of-week adjuster, not null
     */
    public static TemporalAdjuster next(DayOfWeek dayOfWeek) {
        int dowValue = dayOfWeek.getValue();
        return (temporal) -> {
            int calDow = temporal.get(DAY_OF_WEEK);
            int daysDiff = calDow - dowValue;
            return temporal.plus(daysDiff >= 0 ? 7 - daysDiff : -daysDiff, DAYS);
        };
    }

    
Returns the next-or-same day-of-week adjuster, which adjusts the date to the
first occurrence of the specified day-of-week after the date being adjusted
unless it is already on that day in which case the same object is returned.


The ISO calendar system behaves as follows:

The input 2011-01-15 (a Saturday) for parameter (MONDAY) will return 2011-01-17 (two days later).

The input 2011-01-15 (a Saturday) for parameter (WEDNESDAY) will return 2011-01-19 (four days later).

The input 2011-01-15 (a Saturday) for parameter (SATURDAY) will return 2011-01-15 (same as input).

 The behavior is suitable for use with most calendar systems. It uses the DAY_OF_WEEK field and the DAYS unit, and assumes a seven day week. 
Params:
  • dayOfWeek –  the day-of-week to check for or move the date to, not null
Returns:the next-or-same day-of-week adjuster, not null
/**
     * Returns the next-or-same day-of-week adjuster, which adjusts the date to the
     * first occurrence of the specified day-of-week after the date being adjusted
     * unless it is already on that day in which case the same object is returned.
     * <p>
     * The ISO calendar system behaves as follows:<br>
     * The input 2011-01-15 (a Saturday) for parameter (MONDAY) will return 2011-01-17 (two days later).<br>
     * The input 2011-01-15 (a Saturday) for parameter (WEDNESDAY) will return 2011-01-19 (four days later).<br>
     * The input 2011-01-15 (a Saturday) for parameter (SATURDAY) will return 2011-01-15 (same as input).
     * <p>
     * The behavior is suitable for use with most calendar systems.
     * It uses the {@code DAY_OF_WEEK} field and the {@code DAYS} unit,
     * and assumes a seven day week.
     *
     * @param dayOfWeek  the day-of-week to check for or move the date to, not null
     * @return the next-or-same day-of-week adjuster, not null
     */
    public static TemporalAdjuster nextOrSame(DayOfWeek dayOfWeek) {
        int dowValue = dayOfWeek.getValue();
        return (temporal) -> {
            int calDow = temporal.get(DAY_OF_WEEK);
            if (calDow == dowValue) {
                return temporal;
            }
            int daysDiff = calDow - dowValue;
            return temporal.plus(daysDiff >= 0 ? 7 - daysDiff : -daysDiff, DAYS);
        };
    }

    
Returns the previous day-of-week adjuster, which adjusts the date to the
first occurrence of the specified day-of-week before the date being adjusted.


The ISO calendar system behaves as follows:

The input 2011-01-15 (a Saturday) for parameter (MONDAY) will return 2011-01-10 (five days earlier).

The input 2011-01-15 (a Saturday) for parameter (WEDNESDAY) will return 2011-01-12 (three days earlier).

The input 2011-01-15 (a Saturday) for parameter (SATURDAY) will return 2011-01-08 (seven days earlier).

 The behavior is suitable for use with most calendar systems. It uses the DAY_OF_WEEK field and the DAYS unit, and assumes a seven day week. 
Params:
  • dayOfWeek –  the day-of-week to move the date to, not null
Returns:the previous day-of-week adjuster, not null
/**
     * Returns the previous day-of-week adjuster, which adjusts the date to the
     * first occurrence of the specified day-of-week before the date being adjusted.
     * <p>
     * The ISO calendar system behaves as follows:<br>
     * The input 2011-01-15 (a Saturday) for parameter (MONDAY) will return 2011-01-10 (five days earlier).<br>
     * The input 2011-01-15 (a Saturday) for parameter (WEDNESDAY) will return 2011-01-12 (three days earlier).<br>
     * The input 2011-01-15 (a Saturday) for parameter (SATURDAY) will return 2011-01-08 (seven days earlier).
     * <p>
     * The behavior is suitable for use with most calendar systems.
     * It uses the {@code DAY_OF_WEEK} field and the {@code DAYS} unit,
     * and assumes a seven day week.
     *
     * @param dayOfWeek  the day-of-week to move the date to, not null
     * @return the previous day-of-week adjuster, not null
     */
    public static TemporalAdjuster previous(DayOfWeek dayOfWeek) {
        int dowValue = dayOfWeek.getValue();
        return (temporal) -> {
            int calDow = temporal.get(DAY_OF_WEEK);
            int daysDiff = dowValue - calDow;
            return temporal.minus(daysDiff >= 0 ? 7 - daysDiff : -daysDiff, DAYS);
        };
    }

    
Returns the previous-or-same day-of-week adjuster, which adjusts the date to the
first occurrence of the specified day-of-week before the date being adjusted
unless it is already on that day in which case the same object is returned.


The ISO calendar system behaves as follows:

The input 2011-01-15 (a Saturday) for parameter (MONDAY) will return 2011-01-10 (five days earlier).

The input 2011-01-15 (a Saturday) for parameter (WEDNESDAY) will return 2011-01-12 (three days earlier).

The input 2011-01-15 (a Saturday) for parameter (SATURDAY) will return 2011-01-15 (same as input).

 The behavior is suitable for use with most calendar systems. It uses the DAY_OF_WEEK field and the DAYS unit, and assumes a seven day week. 
Params:
  • dayOfWeek –  the day-of-week to check for or move the date to, not null
Returns:the previous-or-same day-of-week adjuster, not null
/**
     * Returns the previous-or-same day-of-week adjuster, which adjusts the date to the
     * first occurrence of the specified day-of-week before the date being adjusted
     * unless it is already on that day in which case the same object is returned.
     * <p>
     * The ISO calendar system behaves as follows:<br>
     * The input 2011-01-15 (a Saturday) for parameter (MONDAY) will return 2011-01-10 (five days earlier).<br>
     * The input 2011-01-15 (a Saturday) for parameter (WEDNESDAY) will return 2011-01-12 (three days earlier).<br>
     * The input 2011-01-15 (a Saturday) for parameter (SATURDAY) will return 2011-01-15 (same as input).
     * <p>
     * The behavior is suitable for use with most calendar systems.
     * It uses the {@code DAY_OF_WEEK} field and the {@code DAYS} unit,
     * and assumes a seven day week.
     *
     * @param dayOfWeek  the day-of-week to check for or move the date to, not null
     * @return the previous-or-same day-of-week adjuster, not null
     */
    public static TemporalAdjuster previousOrSame(DayOfWeek dayOfWeek) {
        int dowValue = dayOfWeek.getValue();
        return (temporal) -> {
            int calDow = temporal.get(DAY_OF_WEEK);
            if (calDow == dowValue) {
                return temporal;
            }
            int daysDiff = dowValue - calDow;
            return temporal.minus(daysDiff >= 0 ? 7 - daysDiff : -daysDiff, DAYS);
        };
    }

}