JAVA獲取某個月(當月)第一天的開始時刻和某個月(當月)最后一天的最后時刻

 

 

package com.date;

import java.text.SimpleDateFormat;
import java.util.Calendar;

public class Test {

    /**
     * 獲取某個月第一天的開始時刻
     * @param month
     * @return
     */
    public static String getFirstDayTimeOfMonth(int month) {
        Calendar cal = Calendar.getInstance();
        // 設置月份
        cal.set(Calendar.MONTH, month - 1);
        // 獲取某月最小天數
        int firstDay = cal.getActualMinimum(Calendar.DAY_OF_MONTH);
        // 設置日歷中月份的最小天數
        cal.set(Calendar.DAY_OF_MONTH, firstDay);
        // 格式化日期，獲取開始時刻
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        String firstDayOfMonth = sdf.format(cal.getTime()) + " 00:00:00";
        return firstDayOfMonth;
    }

    /**
     * 獲得某月的最后一天的最后時刻
     * @param month  要獲取的月份
     * @return
     */
    public static String getLastDayTimeOfMonth(int month) {
        Calendar cal = Calendar.getInstance();
        // 設置月份
        cal.set(Calendar.MONTH, month - 1);
        // 獲取月份的最大天數
        int lastDay = 0;
        //2月份每年的天數不固定
        if (month == 2) {
            lastDay = cal.getLeastMaximum(Calendar.DAY_OF_MONTH);
        } else {
            lastDay = cal.getActualMaximum(Calendar.DAY_OF_MONTH);
        }
        // 設置日歷中月份的最大天數
        cal.set(Calendar.DAY_OF_MONTH, lastDay);
        // 格式化日期，獲取最后時刻
        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();
        //獲取當前月份
        int month = cal.get(Calendar.MONTH) + 1;
        System.out.println(month);
        System.out.println(getFirstDayTimeOfMonth(month));
        System.out.println(getLastDayTimeOfMonth(month));
    }
}