How to Get the Start and the End Date of a Year using Java (#14493)

* How to Get the Start and the End Date of a Year using Java

* How to Get the Start and the End Date of a Year using Java

* How to Get the Start and the End Date of a Year using Java

core-java-modules/core-java-date-operations-3/src/test/java/com/baeldung/firstandlastdayofyear/FirstAndLastDayOfYearUnitTest.java

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+package com.baeldung.firstandlastdayofyear;
+
+import static org.junit.Assert.assertEquals;
+
+import java.text.SimpleDateFormat;
+import java.time.DayOfWeek;
+import java.time.LocalDate;
+import java.time.Month;
+import java.util.Calendar;
+import java.util.Date;
+import org.junit.jupiter.api.Test;
+
+import static java.time.temporal.TemporalAdjusters.firstDayOfYear;
+import static java.time.temporal.TemporalAdjusters.lastDayOfYear;
+
+public class FirstAndLastDayOfYearUnitTest {
+
+    @Test
+    public void givenCurrentDate_whenGettingFirstAndLastDayOfYear_thenCorrectDatesReturned() {
+        LocalDate today = LocalDate.now();
+        LocalDate firstDay = today.with(firstDayOfYear());
+        LocalDate lastDay = today.with(lastDayOfYear());
+
+        assertEquals("2023-01-01", firstDay.toString());
+        assertEquals("2023-12-31", lastDay.toString());
+    }
+
+    @Test
+    public void givenCalendarSetToFirstDayOfYear_whenFormattingDateToISO8601_thenFormattedDateMatchesFirstDay() {
+        Calendar cal = Calendar.getInstance();
+        cal.set(Calendar.YEAR, 2023);
+        cal.set(Calendar.DAY_OF_YEAR, 1);
+        Date firstDay = cal.getTime();
+
+        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
+        String formattedDate = sdf.format(firstDay);
+
+        assertEquals("2023-01-01", formattedDate);
+    }
+
+    @Test
+    public void givenCalendarSetToFirstDayOfYear_whenFormattingDateToISO8601_thenFormattedDateMatchesLastDay() {
+        Calendar cal = Calendar.getInstance();
+        cal.set(Calendar.YEAR, 2023);
+        cal.set(Calendar.MONTH, 11);
+        cal.set(Calendar.DAY_OF_MONTH, 31);
+        Date lastDay = cal.getTime();
+
+        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
+        String formattedDate = sdf.format(lastDay);
+
+        assertEquals("2023-12-31", formattedDate);
+    }
+
+}