java 本月 第一天 至 第七天 用 Calendar实现

以下是实现java本月第一天至第七天的代码，使用了Calendar类：

import java.util.Calendar;

public class Main {
  public static void main(String[] args) {
    Calendar cal = Calendar.getInstance();
    cal.set(Calendar.DAY_OF_MONTH, 1);
    int month = cal.get(Calendar.MONTH) + 1; // 获取当前月份（注意：月份从0开始计数）
    
    // 输出本月第一天
    System.out.println("本月第一天：" + month + "-" + cal.get(Calendar.DAY_OF_MONTH));
    
    // 输出本月第二天至第七天
    for (int i = 2; i <= 7; i++) {
      cal.add(Calendar.DAY_OF_MONTH, 1);
      System.out.println("本月第" + i + "天：" + month + "-" + cal.get(Calendar.DAY_OF_MONTH));
    }
  }
}

运行结果如下：

本月第一天：8-1
本月第2天：8-2
本月第3天：8-3
本月第4天：8-4
本月第5天：8-5
本月第6天：8-6
本月第7天：8-7

相关问题

使用Java编程和springboot和mybatis框架,连接mysql数据库,给出具体程序,包含Controller层、Service层、Service实现类、Dao层以及Mapper.xml文件,统计本周第一天 本月第一天 本年第一天起到今天为止的中奖趋势接口 并对接口使用redis进行缓存处理 过期时间10分钟

首先，需要添加相关依赖：

<!-- Spring Boot Starter -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter</artifactId>
</dependency>

<!-- Spring Boot Starter Web -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>

<!-- Spring Boot Starter Data JDBC -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-jdbc</artifactId>
</dependency>

<!-- MySQL Connector -->
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
</dependency>

<!-- MyBatis -->
<dependency>
    <groupId>org.mybatis.spring.boot</groupId>
    <artifactId>mybatis-spring-boot-starter</artifactId>
    <version>2.2.0</version>
</dependency>

<!-- Redis -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-redis</artifactId>
</dependency>

接下来，创建相关类：

1. Trend.java

public class Trend {
    private String date;
    private int count;

    public String getDate() {
        return date;
    }

    public void setDate(String date) {
        this.date = date;
    }

    public int getCount() {
        return count;
    }

    public void setCount(int count) {
        this.count = count;
    }
}

2. TrendMapper.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
    "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.example.lottery.mapper.TrendMapper">

    <resultMap id="TrendMap" type="com.example.lottery.entity.Trend">
        <result column="date" property="date" jdbcType="VARCHAR" />
        <result column="count" property="count" jdbcType="INTEGER" />
    </resultMap>

    <select id="selectTrend" resultMap="TrendMap">
        SELECT DATE_FORMAT(lottery_time, '%Y-%m-%d') as date, COUNT(*) as count
        FROM lottery
        WHERE lottery_time BETWEEN #{weekBegin} AND NOW()
        GROUP BY DATE_FORMAT(lottery_time, '%Y-%m-%d')
        ORDER BY DATE_FORMAT(lottery_time, '%Y-%m-%d') DESC
    </select>

</mapper>

3. TrendMapper.java

@Mapper
public interface TrendMapper {
    List<Trend> selectTrend(@Param("weekBegin") Date weekBegin);
}

4. TrendService.java

public interface TrendService {
    List<Trend> getTrend();
}

5. TrendServiceImpl.java

@Service
public class TrendServiceImpl implements TrendService {
    @Autowired
    private TrendMapper trendMapper;

    @Autowired
    private RedisTemplate<String, List<Trend>> redisTemplate;

    @Override
    public List<Trend> getTrend() {
        String key = "trend";
        List<Trend> trendList = redisTemplate.opsForValue().get(key);
        if (trendList != null) {
            return trendList;
        }
        Date weekBegin = getWeekBegin();
        trendList = trendMapper.selectTrend(weekBegin);
        redisTemplate.opsForValue().set(key, trendList, Duration.ofMinutes(10));
        return trendList;
    }

    private Date getWeekBegin() {
        Calendar cal = Calendar.getInstance();
        cal.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY);
        cal.set(Calendar.HOUR_OF_DAY, 0);
        cal.set(Calendar.MINUTE, 0);
        cal.set(Calendar.SECOND, 0);
        cal.set(Calendar.MILLISECOND, 0);
        return cal.getTime();
    }
}

6. TrendController.java

@RestController
@RequestMapping("/trend")
public class TrendController {
    @Autowired
    private TrendService trendService;

    @GetMapping
    public List<Trend> getTrend() {
        return trendService.getTrend();
    }
}

7. RedisConfig.java

@Configuration
public class RedisConfig {
    @Bean
    public RedisTemplate<String, List<Trend>> redisTemplate(RedisConnectionFactory factory) {
        RedisTemplate<String, List<Trend>> redisTemplate = new RedisTemplate<>();
        redisTemplate.setConnectionFactory(factory);
        redisTemplate.setKeySerializer(new StringRedisSerializer());
        redisTemplate.setValueSerializer(new Jackson2JsonRedisSerializer<>(List.class));
        return redisTemplate;
    }
}

最后，修改application.properties或application.yml配置文件，添加数据库和Redis相关配置。

注意，以上代码仅供参考，具体实现可能需要根据实际情况进行调整。

用java写一个控制台输入年月日，打印出本月日历

好的，以下是Java代码实现：

import java.util.*;

public class PrintCalendar {

    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        System.out.print("请输入日期（格式：2022-01）：");
        String str = input.nextLine(); // 例如输入：2022-01
        String[] arr = str.split("-");
        int year = Integer.parseInt(arr[0]);
        int month = Integer.parseInt(arr[1]);
        input.close();
        // 获取当月的天数和第一天是星期几
        int days = getDaysOfMonth(year, month);
        int firstDayOfWeek = getFirstDayOfWeek(year, month);
        // 输出日历
        System.out.println("日\t一\t二\t三\t四\t五\t六");
        for (int i = 1; i <= days; i++) {
            if (i == 1) {
                for (int j = 0; j < firstDayOfWeek; j++) {
                    System.out.print("\t");
                }
            }
            System.out.print(i + "\t");
            if ((i + firstDayOfWeek) % 7 == 0) {
                System.out.println();
            }
        }
    }

    // 获取当月的天数
    public static int getDaysOfMonth(int year, int month) {
        int days = 0;
        if (month == 2) {
            days = year % 4 == 0 && year % 100 != 0 || year % 400 == 0 ? 29 : 28;
        } else if (month == 4 || month == 6 || month == 9 || month == 11) {
            days = 30;
        } else {
            days = 31;
        }
        return days;
    }

    // 获取当月第一天是星期几（星期日为0，星期一为1，...，星期六为6）
    public static int getFirstDayOfWeek(int year, int month) {
        Calendar c = Calendar.getInstance();
        c.set(year, month - 1, 1);
        return c.get(Calendar.DAY_OF_WEEK) - 1; // 对应上面的0~6
    }

}

使用示例：

请输入日期（格式：2022-01）：2022-01
日	一	二	三	四	五	六
					1	
2	3	4	5	6	7	8	
9	10	11	12	13	14	15	
16	17	18	19	20	21	22	
23	24	25	26	27	28	29	
30	31