日期的几种用法

1、获取本周一日期

private String getMondayOfThisWeek() {
    SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
    Calendar cur = Calendar.getInstance();
    int day_of_week = cur.get(Calendar.DAY_OF_WEEK) - 1;
    if (day_of_week == 0)   day_of_week = 7;
    cur.add(Calendar.DATE, -day_of_week + 1);
    return sdf.format(cur.getTime());
}

2、获取本月一号日期

private String getFirstdayfoThisMonth() {

    SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
    Calendar cur = Calendar.getInstance();
    cur.set(Calendar.DAY_OF_MONTH, 1); // 1号的日期
    return sdf.format(cur.getTime());
}

3、获取一段时间

private String getTime() {  
    SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
    Calendar cur = Calendar.getInstance();  
    String dateNow = sdf.format(cur.getTime()); //今天的日期
//  cur.add(Calendar.DAY_OF_YEAR, -1);  //一天
//  cur.add(Calendar.WEEK_OF_YEAR, -1); //一周
    cur.add(Calendar.MONTH, -1);            //一月之前的日期
    Date dateFrom = cur.getTime();;
    return (sdf.format(cur.getTime())+"到"+dateNow);     
}

4、获取一个月之前的日期

private String getRecentMonth() {
    SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
    Calendar cur = Calendar.getInstance();
    cur.add(Calendar.MONTH, -1);
    return sdf.format(cur.getTime());
}

5、获取一年之前的日期

private String getRecentYear() {
    SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
    Calendar cur = Calendar.getInstance();
    cur.add(Calendar.YEAR, -1);
    return sdf.format(cur.getTime());
}

6、Calendar Vs java.util.Date 区别？