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/*
* This file is available under and governed by the GNU General Public
* License version 2 only, as published by the Free Software Foundation.
* However, the following notice accompanied the original version of this
* file:
*
* Copyright (c) 2012, Stephen Colebourne & Michael Nascimento Santos
*
* All rights reserved.
*
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package java.time.chrono;
import static java.time.temporal.ChronoField.ERA;
import static java.time.temporal.ChronoUnit.ERAS;
import java.time.DateTimeException;
import java.time.temporal.UnsupportedTemporalTypeException;
import java.time.format.DateTimeFormatterBuilder;
import java.time.format.TextStyle;
import java.time.temporal.ChronoField;
import java.time.temporal.Temporal;
import java.time.temporal.TemporalAccessor;
import java.time.temporal.TemporalAdjuster;
import java.time.temporal.TemporalField;
import java.time.temporal.TemporalQueries;
import java.time.temporal.TemporalQuery;
import java.time.temporal.ValueRange;
import java.util.Locale;
/**
* An era of the time-line.
*
* Most calendar systems have a single epoch dividing the time-line into two eras.
* However, some calendar systems, have multiple eras, such as one for the reign
* of each leader.
* In all cases, the era is conceptually the largest division of the time-line.
* Each chronology defines the Era's that are known Eras and a
* {@link Chronology#eras Chronology.eras} to get the valid eras.
*
* For example, the Thai Buddhist calendar system divides time into two eras,
* before and after a single date. By contrast, the Japanese calendar system
* has one era for the reign of each Emperor.
*
* Instances of {@code Era} may be compared using the {@code ==} operator.
*
* @implSpec
* This interface must be implemented with care to ensure other classes operate correctly.
* All implementations must be singletons - final, immutable and thread-safe.
* It is recommended to use an enum whenever possible.
*
* @since 1.8
*/
public interface Era extends TemporalAccessor, TemporalAdjuster {
/**
* Gets the numeric value associated with the era as defined by the chronology.
* Each chronology defines the predefined Eras and methods to list the Eras
* of the chronology.
*
* All fields, including eras, have an associated numeric value.
* The meaning of the numeric value for era is determined by the chronology
* according to these principles:
*
* - The era in use at the epoch 1970-01-01 (ISO) has the value 1.
*
- Later eras have sequentially higher values.
*
- Earlier eras have sequentially lower values, which may be negative.
*
*
* @return the numeric era value
*/
int getValue();
//-----------------------------------------------------------------------
/**
* Checks if the specified field is supported.
*
* This checks if this era can be queried for the specified field.
* If false, then calling the {@link #range(TemporalField) range} and
* {@link #get(TemporalField) get} methods will throw an exception.
*
* If the field is a {@link ChronoField} then the query is implemented here.
* The {@code ERA} field returns true.
* All other {@code ChronoField} instances will return false.
*
* If the field is not a {@code ChronoField}, then the result of this method
* is obtained by invoking {@code TemporalField.isSupportedBy(TemporalAccessor)}
* passing {@code this} as the argument.
* Whether the field is supported is determined by the field.
*
* @param field the field to check, null returns false
* @return true if the field is supported on this era, false if not
*/
@Override
default boolean isSupported(TemporalField field) {
if (field instanceof ChronoField) {
return field == ERA;
}
return field != null && field.isSupportedBy(this);
}
/**
* Gets the range of valid values for the specified field.
*
* The range object expresses the minimum and maximum valid values for a field.
* This era is used to enhance the accuracy of the returned range.
* If it is not possible to return the range, because the field is not supported
* or for some other reason, an exception is thrown.
*
* If the field is a {@link ChronoField} then the query is implemented here.
* The {@code ERA} field returns the range.
* All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}.
*
* If the field is not a {@code ChronoField}, then the result of this method
* is obtained by invoking {@code TemporalField.rangeRefinedBy(TemporalAccessor)}
* passing {@code this} as the argument.
* Whether the range can be obtained is determined by the field.
*
* The default implementation must return a range for {@code ERA} from
* zero to one, suitable for two era calendar systems such as ISO.
*
* @param field the field to query the range for, not null
* @return the range of valid values for the field, not null
* @throws DateTimeException if the range for the field cannot be obtained
* @throws UnsupportedTemporalTypeException if the unit is not supported
*/
@Override // override for Javadoc
default ValueRange range(TemporalField field) {
return TemporalAccessor.super.range(field);
}
/**
* Gets the value of the specified field from this era as an {@code int}.
*
* This queries this era for the value of the specified field.
* The returned value will always be within the valid range of values for the field.
* If it is not possible to return the value, because the field is not supported
* or for some other reason, an exception is thrown.
*
* If the field is a {@link ChronoField} then the query is implemented here.
* The {@code ERA} field returns the value of the era.
* All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}.
*
* If the field is not a {@code ChronoField}, then the result of this method
* is obtained by invoking {@code TemporalField.getFrom(TemporalAccessor)}
* passing {@code this} as the argument. Whether the value can be obtained,
* and what the value represents, is determined by the field.
*
* @param field the field to get, not null
* @return the value for the field
* @throws DateTimeException if a value for the field cannot be obtained or
* the value is outside the range of valid values for the field
* @throws UnsupportedTemporalTypeException if the field is not supported or
* the range of values exceeds an {@code int}
* @throws ArithmeticException if numeric overflow occurs
*/
@Override // override for Javadoc and performance
default int get(TemporalField field) {
if (field == ERA) {
return getValue();
}
return TemporalAccessor.super.get(field);
}
/**
* Gets the value of the specified field from this era as a {@code long}.
*
* This queries this era for the value of the specified field.
* If it is not possible to return the value, because the field is not supported
* or for some other reason, an exception is thrown.
*
* If the field is a {@link ChronoField} then the query is implemented here.
* The {@code ERA} field returns the value of the era.
* All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}.
*
* If the field is not a {@code ChronoField}, then the result of this method
* is obtained by invoking {@code TemporalField.getFrom(TemporalAccessor)}
* passing {@code this} as the argument. Whether the value can be obtained,
* and what the value represents, is determined by the field.
*
* @param field the field to get, not null
* @return the value for the field
* @throws DateTimeException if a value for the field cannot be obtained
* @throws UnsupportedTemporalTypeException if the field is not supported
* @throws ArithmeticException if numeric overflow occurs
*/
@Override
default long getLong(TemporalField field) {
if (field == ERA) {
return getValue();
} else if (field instanceof ChronoField) {
throw new UnsupportedTemporalTypeException("Unsupported field: " + field);
}
return field.getFrom(this);
}
//-----------------------------------------------------------------------
/**
* Queries this era using the specified query.
*
* This queries this era using the specified query strategy object.
* The {@code TemporalQuery} object defines the logic to be used to
* obtain the result. Read the documentation of the query to understand
* what the result of this method will be.
*
* The result of this method is obtained by invoking the
* {@link TemporalQuery#queryFrom(TemporalAccessor)} method on the
* specified query passing {@code this} as the argument.
*
* @param the type of the result
* @param query the query to invoke, not null
* @return the query result, null may be returned (defined by the query)
* @throws DateTimeException if unable to query (defined by the query)
* @throws ArithmeticException if numeric overflow occurs (defined by the query)
*/
@SuppressWarnings("unchecked")
@Override
default R query(TemporalQuery query) {
if (query == TemporalQueries.precision()) {
return (R) ERAS;
}
return TemporalAccessor.super.query(query);
}
/**
* Adjusts the specified temporal object to have the same era as this object.
*
* This returns a temporal object of the same observable type as the input
* with the era changed to be the same as this.
*
* The adjustment is equivalent to using {@link Temporal#with(TemporalField, long)}
* passing {@link ChronoField#ERA} as the field.
*
* In most cases, it is clearer to reverse the calling pattern by using
* {@link Temporal#with(TemporalAdjuster)}:
*
* // these two lines are equivalent, but the second approach is recommended
* temporal = thisEra.adjustInto(temporal);
* temporal = temporal.with(thisEra);
*
*
* This instance is immutable and unaffected by this method call.
*
* @param temporal the target object to be adjusted, not null
* @return the adjusted object, not null
* @throws DateTimeException if unable to make the adjustment
* @throws ArithmeticException if numeric overflow occurs
*/
@Override
default Temporal adjustInto(Temporal temporal) {
return temporal.with(ERA, getValue());
}
//-----------------------------------------------------------------------
/**
* Gets the textual representation of this era.
*
* This returns the textual name used to identify the era,
* suitable for presentation to the user.
* The parameters control the style of the returned text and the locale.
*
* If no textual mapping is found then the {@link #getValue() numeric value} is returned.
*
* This default implementation is suitable for all implementations.
*
* @param style the style of the text required, not null
* @param locale the locale to use, not null
* @return the text value of the era, not null
*/
default String getDisplayName(TextStyle style, Locale locale) {
return new DateTimeFormatterBuilder().appendText(ERA, style).toFormatter(locale).format(this);
}
// NOTE: methods to convert year-of-era/proleptic-year cannot be here as they may depend on month/day (Japanese)
}