BAEL-6595 code for the How Many Days Are There in a Particular Month of a Given Year article

core-java-modules/core-java-8-datetime-2/src/main/java/com/baeldung/daysinmonth/DaysInMonthUtils.java

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+package com.baeldung.daysinmonth;
+
+import java.time.YearMonth;
+import java.util.Calendar;
+
+public class DaysInMonthUtils {
+
+    public int getDaysInMonthWithYearOfMonth(int month, int year) {
+        YearMonth yearMonth = YearMonth.of(year, month);
+        return yearMonth.lengthOfMonth();
+    }
+
+    public int getDaysInMonthWithCalendar(int month, int year) {
+        Calendar calendar = Calendar.getInstance();
+        calendar.set(Calendar.DAY_OF_MONTH, 1);
+        calendar.set(Calendar.YEAR, year);
+        calendar.set(Calendar.MONTH, month - 1);
+        return calendar.getActualMaximum(Calendar.DATE);
+    }
+
+}

core-java-modules/core-java-8-datetime-2/src/test/java/com/baeldung/daysinmonth/DaysInMonthUtilsUnitTest.java

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+package com.baeldung.daysinmonth;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+class DaysInMonthUtilsUnitTest {
+
+    @Test
+    void whenGetDaysInMonthWithYearOfMonth_thenCorrectResult() {
+        assertEquals(31, new DaysInMonthUtils().getDaysInMonthWithYearOfMonth(3, 2024));
+        assertEquals(30, new DaysInMonthUtils().getDaysInMonthWithYearOfMonth(11, 1999));
+        assertEquals(28, new DaysInMonthUtils().getDaysInMonthWithYearOfMonth(2, 2025));
+        assertEquals(29, new DaysInMonthUtils().getDaysInMonthWithYearOfMonth(2, 2004));
+    }
+
+    @Test
+    void whenGetDaysInMonthWithCalendar_thenCorrectResult() {
+        assertEquals(31, new DaysInMonthUtils().getDaysInMonthWithCalendar(3, 2024));
+        assertEquals(30, new DaysInMonthUtils().getDaysInMonthWithCalendar(11, 1999));
+        assertEquals(28, new DaysInMonthUtils().getDaysInMonthWithCalendar(2, 2025));
+        assertEquals(29, new DaysInMonthUtils().getDaysInMonthWithCalendar(2, 2004));
+    }
+
+}