package com.date;

import java.text.SimpleDateFormat;

import java.util.Calendar;

public class Test {

    /**

     * 获取某个月第一天的开始时刻

     * @param month

     * @return

     */

    public static String getFirstDayTimeOfMonth(int month) {

        Calendar cal = Calendar.getInstance();

        // 设置月份

        cal.set(Calendar.MONTH, month - 1);

        // 获取某月最小天数

        int firstDay = cal.getActualMinimum(Calendar.DAY_OF_MONTH);

        // 设置日历中月份的最小天数

        cal.set(Calendar.DAY_OF_MONTH, firstDay);

        // 格式化日期，获取开始时刻

        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");

        String firstDayOfMonth = sdf.format(cal.getTime()) + " 00:00:00";

        return firstDayOfMonth;

    }

    /**

     * 获得某月的最后一天的最后时刻

     * @param month  要获取的月份

     * @return

     */

    public static String getLastDayTimeOfMonth(int month) {

        Calendar cal = Calendar.getInstance();

        // 设置月份

        cal.set(Calendar.MONTH, month - 1);

        // 获取月份的最大天数

        int lastDay = 0;

        //2月份每年的天数不固定

        if (month == 2) {

            lastDay = cal.getLeastMaximum(Calendar.DAY_OF_MONTH);

        } else {

            lastDay = cal.getActualMaximum(Calendar.DAY_OF_MONTH);

        }

        // 设置日历中月份的最大天数

        cal.set(Calendar.DAY_OF_MONTH, lastDay);

        // 格式化日期，获取最后时刻

        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");

        String lastDayOfMonth = sdf.format(cal.getTime()) + " 23:59:59";

        return lastDayOfMonth;

    }

    public static void main(String[] args) {

        Calendar cal = Calendar.getInstance();

        //获取当前月份

        int month = cal.get(Calendar.MONTH) + 1;

        System.out.println(month);

        System.out.println(getFirstDayTimeOfMonth(month));

        System.out.println(getLastDayTimeOfMonth(month));

    }

}