Code examples for Java 8 date migration (#460)

core-java-8/src/main/java/com/baeldung/date_migration/Conversion.java

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+package com.baeldung.date_migration;
+
+import java.time.Instant;
+import java.time.ZoneId;
+import java.time.ZonedDateTime;
+import java.util.Date;
+import java.util.GregorianCalendar;
+import java.util.TimeZone;
+
+public class Conversion {
+    public static void main(String[] args) {
+        Instant instantFromCalendar = GregorianCalendar.getInstance().toInstant();
+        ZonedDateTime zonedDateTimeFromCalendar = new GregorianCalendar().toZonedDateTime();
+        Date dateFromInstant = Date.from(Instant.now());
+        GregorianCalendar calendarFromZonedDateTime = GregorianCalendar.from(ZonedDateTime.now());
+        Instant instantFromDate = new Date().toInstant();
+        ZoneId zoneIdFromTimeZone = TimeZone.getTimeZone("PST").toZoneId();
+    }
+}

core-java-8/src/main/java/com/baeldung/date_migration/NewApi.java

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+package com.baeldung.date_migration;
+
+import java.text.ParseException;
+import java.time.*;
+import java.time.format.DateTimeFormatter;
+import java.time.temporal.ChronoUnit;
+
+public class NewApi {
+    public void currentTime() {
+        ZonedDateTime now = ZonedDateTime.now();
+    }
+
+    public void specificTime() {
+        LocalDate birthDay = LocalDate.of(1990, Month.DECEMBER, 15);
+    }
+
+    public void extractMonth() {
+        Month month = LocalDateTime.now().getMonth();
+    }
+
+    public void subtractTime() {
+        LocalDateTime fiveHoursBefore = LocalDateTime.now().minusHours(5);
+    }
+
+    public void alterField() {
+        LocalDateTime inJune = LocalDateTime.now().withMonth(Month.JUNE.getValue());
+    }
+
+    public void truncate() {
+        LocalTime truncated = LocalTime.now().truncatedTo(ChronoUnit.HOURS);
+    }
+
+    public void convertTimeZone() {
+        ZonedDateTime centralEastern = LocalDateTime.now().atZone(ZoneId.of("CET"));
+    }
+
+    public void getTimeSpan() {
+        LocalDateTime now = LocalDateTime.now();
+        LocalDateTime hourLater = LocalDateTime.now().plusHours(1);
+        Duration span = Duration.between(now, hourLater);
+    }
+
+    public void formatAndParse() throws ParseException {
+        LocalDate now = LocalDate.now();
+        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd");
+        String formattedDate = now.format(formatter);
+        LocalDate parsedDate = LocalDate.parse(formattedDate, formatter);
+    }
+
+    public void daysInMonth() {
+        int daysInMonth = YearMonth.of(1990, 2).lengthOfMonth();
+    }
+
+}

core-java-8/src/main/java/com/baeldung/date_migration/OldApi.java

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+package com.baeldung.date_migration;
+
+import java.text.ParseException;
+import java.text.SimpleDateFormat;
+import java.util.Calendar;
+import java.util.Date;
+import java.util.GregorianCalendar;
+import java.util.TimeZone;
+
+public class OldApi {
+    public void currentTime() {
+        Date now = new Date();
+    }
+
+    public void specificTime () {
+        Date birthDay = new GregorianCalendar(1990, Calendar.DECEMBER, 15).getTime();
+    }
+
+    public void extractMonth() {
+        int month = new GregorianCalendar().get(Calendar.MONTH);
+    }
+
+    public void subtractTime() {
+        GregorianCalendar calendar = new GregorianCalendar();
+        calendar.add(Calendar.HOUR_OF_DAY, -5);
+        Date fiveHoursBefore = calendar.getTime();
+    }
+
+    public void alterField() {
+        GregorianCalendar calendar = new GregorianCalendar();
+        calendar.set(Calendar.MONTH, Calendar.JUNE);
+        Date inJune = calendar.getTime();
+    }
+
+    public void truncate() {
+        Calendar now = Calendar.getInstance();
+        now.set(Calendar.MINUTE, 0);
+        now.set(Calendar.SECOND, 0);
+        now.set(Calendar.MILLISECOND, 0);
+        Date truncated = now.getTime();
+    }
+
+    public void convertTimeZone() {
+        GregorianCalendar calendar = new GregorianCalendar();
+        calendar.setTimeZone(TimeZone.getTimeZone("CET"));
+        Date centralEastern = calendar.getTime();
+    }
+
+    public void getTimeSpan() {
+        GregorianCalendar calendar = new GregorianCalendar();
+        Date now = new Date();
+        calendar.add(Calendar.HOUR, 1);
+        Date hourLater = calendar.getTime();
+        long elapsed = hourLater.getTime() - now.getTime();
+    }
+
+    public void formatAndParse() throws ParseException {
+        SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
+        Date now = new Date();
+        String formattedDate = dateFormat.format(now);
+        Date parsedDate = dateFormat.parse(formattedDate);
+    }
+
+    public void daysInMonth() {
+        Calendar calendar = new GregorianCalendar(1990, Calendar.FEBRUARY, 20);
+        int daysInMonth = calendar.getActualMaximum(Calendar.DAY_OF_MONTH);
+    }
+}