java-日期操作-获得某月（某个时间）第一天的时间和最后一天的时间

package com.landray.kmss.tonly.dormitory.actions;

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

public class demo {
	/**
	 * @param grsc
	 * @throws Exception 
	 */
	public static void main(String[] args) throws Exception
	{
		String datadate = "2016-10-24 21:59:06";
        demo test = new demo();
        //获取第一天
        String first= test.getFirstDay(datadate);
        //获取最后一天
        String last= test.getLastDay(datadate);
        System.out.println("first="+first);
        System.out.println("last="+last);

	}
	
	//获取当月的第一天时间
	public String getFirstDay(String datadate)throws Exception{
		Date date = null;
		String day_first = null;
		SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
		date = format.parse(datadate);
		//创建日历
		Calendar calendar = Calendar.getInstance();
		calendar.setTime(date);
		calendar.set(Calendar.DAY_OF_MONTH, 1);
		day_first = format.format(calendar.getTime());
		return day_first;
     }
	
	//获取当月的最后一天时间
	public String getLastDay(String datadate)throws Exception{
		Date date = null;
		String day_last = null;
		SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
		date = format.parse(datadate);
		
		//创建日历
		Calendar calendar = Calendar.getInstance();
		calendar.setTime(date);
		calendar.add(Calendar.MONTH, 1);//加一个月
        calendar.set(Calendar.DATE, 1);//设置为该月第一天
        calendar.add(Calendar.DATE, -1); //再减一天即为上个月最后一天
        day_last = format.format(calendar.getTime());
        return day_last;
    }

}

输出结果：