From 49929794b8db2ca20239b2dea47b07a3573a468f Mon Sep 17 00:00:00 2001
From: Azhwani <13301425+azhwani@users.noreply.github.com>
Date: Mon, 30 Oct 2023 17:42:44 +0100
Subject: [PATCH] BAEL-7111: Get First Date of Current Month in Java (#15023)

---
 .../FirstDayOfMonthUnitTest.java              | 61 +++++++++++++++++++
 1 file changed, 61 insertions(+)
 create mode 100644 core-java-modules/core-java-date-operations-3/src/test/java/com/baeldung/firstdaymonth/FirstDayOfMonthUnitTest.java

diff --git a/core-java-modules/core-java-date-operations-3/src/test/java/com/baeldung/firstdaymonth/FirstDayOfMonthUnitTest.java b/core-java-modules/core-java-date-operations-3/src/test/java/com/baeldung/firstdaymonth/FirstDayOfMonthUnitTest.java
new file mode 100644
index 0000000000..9edc3e4a8d
--- /dev/null
+++ b/core-java-modules/core-java-date-operations-3/src/test/java/com/baeldung/firstdaymonth/FirstDayOfMonthUnitTest.java
@@ -0,0 +1,61 @@
+package com.baeldung.firstdaymonth;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.time.LocalDate;
+import java.time.YearMonth;
+import java.time.temporal.TemporalAdjusters;
+import java.util.Calendar;
+import java.util.Date;
+import java.util.GregorianCalendar;
+
+import org.junit.jupiter.api.Test;
+
+public class FirstDayOfMonthUnitTest {
+
+    @Test
+    void givenMonth_whenUsingCalendar_thenReturnFirstDay() {
+        Date currentDate = new GregorianCalendar(2023, Calendar.NOVEMBER, 23).getTime();
+        Date expectedDate = new GregorianCalendar(2023, Calendar.NOVEMBER, 1).getTime();
+
+        Calendar cal = Calendar.getInstance();
+        cal.setTime(currentDate);
+        cal.set(Calendar.DAY_OF_MONTH, 1);
+
+        assertEquals(expectedDate, cal.getTime());
+    }
+
+    @Test
+    void givenMonth_whenUsingLocalDate_thenReturnFirstDay() {
+        LocalDate currentDate = LocalDate.of(2023, 9, 6);
+        LocalDate expectedDate = LocalDate.of(2023, 9, 1);
+
+        assertEquals(expectedDate, currentDate.withDayOfMonth(1));
+    }
+
+    @Test
+    void givenMonth_whenUsingTemporalAdjusters_thenReturnFirstDay() {
+        LocalDate currentDate = LocalDate.of(2023, 7, 19);
+        LocalDate expectedDate = LocalDate.of(2023, 7, 1);
+
+        assertEquals(expectedDate, currentDate.with(TemporalAdjusters.firstDayOfMonth()));
+    }
+
+    @Test
+    void givenMonth_whenUsingYearMonth_thenReturnFirstDay() {
+        YearMonth currentDate = YearMonth.of(2023, 4);
+        LocalDate expectedDate = LocalDate.of(2023, 4, 1);
+
+        assertEquals(expectedDate, currentDate.atDay(1));
+    }
+
+    @Test
+    void givenMonth_whenUsingJodaTime_thenReturnFirstDay() {
+        org.joda.time.LocalDate currentDate = org.joda.time.LocalDate.parse("2023-5-10");
+        org.joda.time.LocalDate expectedDate = org.joda.time.LocalDate.parse("2023-5-1");
+
+        assertEquals(expectedDate, currentDate.dayOfMonth()
+          .withMinimumValue());
+    }
+
+}