java 日期获取，每月一号，每周一
package info.lumanman.h5.util;
import java.text.SimpleDateFormat;
import java.util.Calendar;
public class DateUtil {
public static void main(String[] args) {
SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
//addDay(sdf,10);
//getWeekDay(sdf);
getMonth(sdf);
}
/**
* 增加天数
* @param sdf
*/
public static void addDay(SimpleDateFormat sdf,int days){
//获取Calendar实例，java封装的表现，private类Calendar的构造函数，通过静态方法创建对象
Calendar calendar=Calendar.getInstance();
//获取当前时间并格式化
System.out.println("当前时间: "+sdf.format(calendar.getTime()));
//给当前时间加上天数days并输出，这里的第一个参数用以下三个都可以
Calendar calendar1=Calendar.getInstance();
calendar1.add(Calendar.DAY_OF_YEAR, days);
System.out.println("加了"+days+"天之后的时间: "+sdf.format(calendar1.getTime()));
Calendar calendar2=Calendar.getInstance();
calendar2.add(Calendar.DAY_OF_MONTH, days);
System.out.println("加了"+days+"之后的时间: "+sdf.format(calendar2.getTime()));
Calendar calendar3=Calendar.getInstance();
calendar3.add(Calendar.DAY_OF_WEEK, days);
System.out.println("加了"+days+"之后的时间: "+sdf.format(calendar3.getTime()));
}
/**
* 获取当前星期、前一星期、后一星期的第一天和最后一天
* @param sdf
*/
public static void getWeekDay(SimpleDateFormat sdf){
//获取Calendar实例，java封装的表现，private类Calendar的构造函数，通过静态方法创建对象
Calendar calendar=Calendar.getInstance();
//获取当前时间并格式化
System.out.println("当前时间: "+sdf.format(calendar.getTime()));
//本周一
Calendar calendar1=Calendar.getInstance();
calendar1.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY);
System.out.println("本周一: "+sdf.format(calendar1.getTime()));
//本周日
Calendar calendar2=Calendar.getInstance();
//外国的星期天和我们的不在一周(外国是星期天到星期六为一个星期)
calendar2.add(Calendar.DAY_OF_WEEK, 7);
calendar2.set(Calendar.DAY_OF_WEEK, Calendar.SUNDAY);
System.out.println("本周日: "+sdf.format(calendar2.getTime()));
//下周一
Calendar calendar3=Calendar.getInstance();
calendar3.add(Calendar.DAY_OF_MONTH, 7);
calendar3.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY);
System.out.println("下周一: "+sdf.format(calendar3.getTime()));
//下周日
Calendar calendar4=Calendar.getInstance();
calendar4.add(Calendar.DAY_OF_MONTH, 14);
calendar4.set(Calendar.DAY_OF_WEEK, Calendar.SUNDAY);
System.out.println("下周日: "+sdf.format(calendar4.getTime()));
//上周一
Calendar calendar5=Calendar.getInstance();
calendar5.add(Calendar.DAY_OF_YEAR, -7);
calendar5.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY);
System.out.println("上周一: "+sdf.format(calendar5.getTime()));
//上周日
Calendar calendar6=Calendar.getInstance();
calendar6.set(Calendar.DAY_OF_WEEK, Calendar.SUNDAY);
System.out.println("上周日: "+sdf.format(calendar6.getTime()));
}
/**
* 获取当前月、前一月、后一月的第一天和最后一天
* @param sdf
*/
public static void getMonth(SimpleDateFormat sdf){
//定义当前月的总天数，比如30,31,28,29
int maxCurrentMonthDay=0;
Calendar calendar=Calendar.getInstance();
System.out.println("当前时间: "+sdf.format(calendar.getTime()));
//当月一号
Calendar calendar1=Calendar.getInstance();
calendar1.set(Calendar.DAY_OF_MONTH, 1);
System.out.println("本月第一天: "+sdf.format(calendar1.getTime()));
//当月最后一天
Calendar calendar2=Calendar.getInstance();
maxCurrentMonthDay=calendar2.getActualMaximum(Calendar.DAY_OF_MONTH);
calendar2.set(Calendar.DAY_OF_MONTH, maxCurrentMonthDay);
System.out.println("本月最后一天: "+sdf.format(calendar2.getTime()));
//下个月一号
Calendar calendar3=Calendar.getInstance();
maxCurrentMonthDay=calendar3.getActualMaximum(Calendar.DAY_OF_MONTH);
calendar3.add(Calendar.DAY_OF_MONTH, maxCurrentMonthDay);
calendar3.set(Calendar.DAY_OF_MONTH, 1);
System.out.println("下月第一天: "+sdf.format(calendar3.getTime()));
//下个月最后一天
Calendar calendar4=Calendar.getInstance();
maxCurrentMonthDay=calendar4.getActualMaximum(Calendar.DAY_OF_MONTH);
calendar4.add(Calendar.DAY_OF_MONTH, maxCurrentMonthDay);
//第一个maxCurrentMonthDay获取的是当月的天数，第二个maxCurrentMonthDay获取的是下个月的天数
maxCurrentMonthDay=calendar4.getActualMaximum(Calendar.DAY_OF_MONTH);
calendar4.set(Calendar.DAY_OF_MONTH, maxCurrentMonthDay);
System.out.println("下月第一天: "+sdf.format(calendar4.getTime()));
//上个月一号
Calendar calendar5=Calendar.getInstance();
maxCurrentMonthDay=calendar5.getActualMaximum(Calendar.DAY_OF_MONTH);
calendar5.add(Calendar.DAY_OF_MONTH, -maxCurrentMonthDay);
calendar5.set(Calendar.DAY_OF_MONTH, 1);
System.out.println("上月第一天: "+sdf.format(calendar5.getTime()));
//上个月最后一天
Calendar calendar6=Calendar.getInstance();
maxCurrentMonthDay=calendar6.getActualMaximum(Calendar.DAY_OF_MONTH);
calendar6.add(Calendar.DAY_OF_MONTH, -maxCurrentMonthDay);
//第一个maxCurrentMonthDay获取的是当月的天数，第二个maxCurrentMonthDay获取的是上个月的天数
maxCurrentMonthDay=calendar6.getActualMaximum(Calendar.DAY_OF_MONTH);
calendar6.set(Calendar.DAY_OF_MONTH, maxCurrentMonthDay);
System.out.println("上月第一天: "+sdf.format(calendar6.getTime()));
}
}