Java TemporalQuery Tutorial with Examples
1. TemporalQuery
No ADS
The TemporalQuery interface is a tool for querying a TemporalAccessor object to extract information. Basically, TemporalQuery exists to externalize the querying information of the TemporalAccessor object instead of extracting the information directly.
@FunctionalInterface
public interface TemporalQuery<R> {
R queryFrom(TemporalAccessor temporal);
}
Example: We write HourMinuteQuery class to extract hour and minute information as a string "HH:mm" from TemporalAccessor objects.
TemporalAccessor | Example | Using HourMinuteQuery |
LocalDateTime | 2020-11-25 13:30:45 | 13:30 |
ZonedDateTime | 2020-11-25 15:30:45+06:00[Asia/Bishkek] | 15:30 |
LocalTime | 21:45:45 | 21:45 |
HourMinuteQuery.java
package org.o7planning.temporalquery.ex;
import java.time.temporal.ChronoField;
import java.time.temporal.TemporalAccessor;
import java.time.temporal.TemporalQuery;
public class HourMinuteQuery implements TemporalQuery<String> {
@Override
public String queryFrom(TemporalAccessor temporal) {
if (temporal.isSupported(ChronoField.HOUR_OF_DAY) //
&& temporal.isSupported(ChronoField.MINUTE_OF_HOUR)) {
int hour = temporal.get(ChronoField.HOUR_OF_DAY);
int minute = temporal.get(ChronoField.MINUTE_OF_HOUR);
return hour + ":" + minute;
}
return null;
}
}
Using HourMinuteQuery:
HourMinuteQuery_ex1.java
package org.o7planning.temporalquery.ex;
import java.time.ZoneId;
import java.time.ZonedDateTime;
public class HourMinuteQuery_ex1 {
public static void main(String[] args) {
// TemporalAccessor object:
ZonedDateTime parisNow = ZonedDateTime.now(ZoneId.of("Europe/Paris"));
System.out.printf("Paris now is: %s%n", parisNow);
HourMinuteQuery query = new HourMinuteQuery();
String info = query.queryFrom(parisNow);
System.out.println("Info: " + info);
}
}
Output:
Paris now is: 2021-07-05T19:17:54.978689+02:00[Europe/Paris]
Info: 19:17
There are two ways to query a TemporalAccessor object, in which the second approach is recommended.
// These two lines are equivalent, but the second approach is recommended
information = thisQuery.queryFrom(temporalAccessor); // (1)
information = temporalAccessor.query(thisQuery); // (2)
2. Ex: AllLeapYearsInSameDecadeQuery
No ADS
Create a TemporalQuery to search all leap years in the same decade with a TemporalAccessor object.
AllLeapYearsInSameDecadeQuery.java
package org.o7planning.temporalquery.ex;
import java.time.DateTimeException;
import java.time.chrono.ChronoLocalDate;
import java.time.temporal.ChronoField;
import java.time.temporal.TemporalAccessor;
import java.time.temporal.TemporalQuery;
import java.util.ArrayList;
import java.util.List;
// Return all leap years in the same Decade with a TemporalAccessor.
public class AllLeapYearsInSameDecadeQuery implements TemporalQuery<List<Integer>> {
@Override
public List<Integer> queryFrom(TemporalAccessor temporal) {
if (!(temporal instanceof ChronoLocalDate)) {
throw new DateTimeException("Only ChronoLocalDate is supported");
}
List<Integer> leapYears = new ArrayList<>();
ChronoLocalDate localDate = (ChronoLocalDate) temporal;
int year = localDate.get(ChronoField.YEAR);
int firstYearInSameDecade = year - (year % 10);
for (int i = 0; i < 10; i++) {
int y = firstYearInSameDecade + i;
ChronoLocalDate newLocalDate = localDate.with(ChronoField.YEAR, y);
if (newLocalDate.isLeapYear()) {
leapYears.add(newLocalDate.get(ChronoField.YEAR));
}
}
return leapYears;
}
}
AllLeapYearsInSameDecadeQuery_ex1.java
LocalDate today = LocalDate.now();
System.out.println("Today is: " + today);
System.out.println("Year: " + today.getYear());
System.out.printf("Leap years in the same decade with %d:%n%n", today.getYear());
AllLeapYearsInSameDecadeQuery query = new AllLeapYearsInSameDecadeQuery();
// Return leap years in the same decade with today.
List<Integer> leapYears = query.queryFrom(today);
for(Integer leapYear: leapYears) {
System.out.println("Leap year: " + leapYear);
}
Output:
Today is: 2021-07-05
Year: 2021
Leap years in the same decade with 2021:
Leap year: 2020
Leap year: 2024
Leap year: 2028
3. Ex: AllMondaysInSameMonthQuery
No ADS
Create a TemporalQuery to search all Mondays in the same month with a TemporalAccessor object.
AllMondaysInSameMonthQuery.java
package org.o7planning.temporalquery.ex;
import java.time.DateTimeException;
import java.time.LocalDate;
import java.time.temporal.ChronoField;
import java.time.temporal.TemporalAccessor;
import java.time.temporal.TemporalQuery;
import java.time.temporal.ValueRange;
import java.util.ArrayList;
import java.util.List;
public class AllMondaysInSameMonthQuery implements TemporalQuery<List<LocalDate>>{
@Override
public List<LocalDate> queryFrom(TemporalAccessor temporal) {
if(!(temporal instanceof LocalDate)) {
throw new DateTimeException("Only LocalDate is supported");
}
LocalDate localDate = (LocalDate) temporal;
List<LocalDate> retList= new ArrayList<LocalDate>();
ValueRange range = localDate.range(ChronoField.DAY_OF_MONTH);
for(long dayOfMonth = range.getMinimum(); dayOfMonth<= range.getMaximum(); dayOfMonth++) {
LocalDate date = localDate.withDayOfMonth((int) dayOfMonth);
int dayOfWeek = date.get(ChronoField.DAY_OF_WEEK) ;
if(dayOfWeek == 1) { // Monday
retList.add(date);
}
}
return retList;
}
}
AllMondaysInSameMonthQuery_ex1.java
LocalDate localDate = LocalDate.now();
System.out.println("Today is: " + localDate );
System.out.println("All mondays in the same month:\n");
AllMondaysInSameMonthQuery query = new AllMondaysInSameMonthQuery();
// Same as: mondaysInSameMonth = localDate.query(query);
List<LocalDate> mondaysInSameMonth = query.queryFrom(localDate);
for(LocalDate monday: mondaysInSameMonth) {
System.out.println(monday);
}
Output:
Today is: 2021-07-05
All mondays in the same month:
2021-07-05
2021-07-12
2021-07-19
2021-07-26
4. Ex: AllZoneIdsSameOffsetQuery
No ADS
Create a TemporalQuery to search all ZoneId(s) available in the system and with the same zone-offset as a TemporalAccessor object.
AllZoneIdsSameOffsetQuery.java
package org.o7planning.temporalquery.ex;
import java.time.Instant;
import java.time.ZoneId;
import java.time.ZoneOffset;
import java.time.temporal.ChronoField;
import java.time.temporal.TemporalAccessor;
import java.time.temporal.TemporalQuery;
import java.util.ArrayList;
import java.util.List;
import java.util.Set;
// Find all available ZoneIds with the same offset as a TemporalAccessor.
public class AllZoneIdsSameOffsetQuery implements TemporalQuery<List<ZoneId>> {
@Override
public List<ZoneId> queryFrom(TemporalAccessor temporal) {
ZoneOffset offset = ZoneOffset.from(temporal);
List<ZoneId> returnList = new ArrayList<>();
Set<String> zoneIdNames = ZoneId.getAvailableZoneIds();
if (temporal.isSupported(ChronoField.OFFSET_SECONDS)) {
for (String zoneIdName : zoneIdNames) {
ZoneId zid = ZoneId.of(zoneIdName);
ZoneOffset os = zid.getRules().getOffset(Instant.now());
if (offset.compareTo(os) == 0) {
returnList.add(zid);
}
}
}
return returnList;
}
}
AllZoneIdsSameOffsetQuery_ex1.java
ZonedDateTime parisNow = ZonedDateTime.now(ZoneId.of("Europe/Paris"));
System.out.printf("Paris now is: %s%n", parisNow);
System.out.printf("Paris offset: %s%n", parisNow.getOffset());
AllZoneIdsSameOffsetQuery query = new AllZoneIdsSameOffsetQuery();
// Same as: sameOffsetZoneIds = parisNow.query(query);
List<ZoneId> sameOffsetZoneIds = query.queryFrom(parisNow);
System.out.printf("All available ZoneId with the same offset as %s:%n%n",parisNow.getOffset());
for(ZoneId zoneId: sameOffsetZoneIds) {
System.out.println(zoneId.getId() +" : " + zoneId.getRules().getOffset(Instant.now()));
}
Output:
Paris now is: 2021-07-05T17:44:23.310010+02:00[Europe/Paris]
Paris offset: +02:00
All available ZoneId with the same offset as +02:00:
Africa/Cairo : +02:00
Africa/Mbabane : +02:00
Europe/Brussels : +02:00
Africa/Harare : +02:00
.....
Africa/Khartoum : +02:00
Africa/Johannesburg : +02:00
Europe/Belgrade : +02:00
Europe/Bratislava : +02:00
Arctic/Longyearbyen : +02:00
Europe/Monaco : +02:00
No ADS
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