Java - get number of days in month

import org.junit.Test;

import java.time.YearMonth;

import static org.assertj.core.api.Assertions.assertThat;

​

public class MonthUtil {

​

    public static int getMaxDaysInMonth(int year, int month) {

        YearMonth yearMonthObject = YearMonth.of(year, month);

        return yearMonthObject.lengthOfMonth();

    }

​

    @Test

    public void test() {

        {

            int year = 2021;

            int month = 7;

            int maxDaysInMonth = getMaxDaysInMonth(year, month);

            System.out.println(maxDaysInMonth); // 31

        }

​

        assertThat(getMaxDaysInMonth(2021, 1)).isEqualTo(31);

        assertThat(getMaxDaysInMonth(2021, 2)).isEqualTo(28);

        assertThat(getMaxDaysInMonth(2021, 3)).isEqualTo(31);

        assertThat(getMaxDaysInMonth(2021, 4)).isEqualTo(30);

        assertThat(getMaxDaysInMonth(2021, 5)).isEqualTo(31);

        assertThat(getMaxDaysInMonth(2021, 6)).isEqualTo(30);

        assertThat(getMaxDaysInMonth(2021, 7)).isEqualTo(31);

        assertThat(getMaxDaysInMonth(2021, 8)).isEqualTo(31);

        assertThat(getMaxDaysInMonth(2021, 9)).isEqualTo(30);

        assertThat(getMaxDaysInMonth(2021, 10)).isEqualTo(31);

        assertThat(getMaxDaysInMonth(2021, 11)).isEqualTo(30);

        assertThat(getMaxDaysInMonth(2021, 12)).isEqualTo(31);

    }

}

<!-- https://mvnrepository.com/artifact/org.assertj/assertj-core -->

<dependency>

    <groupId>org.assertj</groupId>

    <artifactId>assertj-core</artifactId>

    <version>3.8.0</version>

    <scope>test</scope>

</dependency>