Android 笔记：计算当前日期时间前后几天的封装方法

/**
 * 得到几天前的时间
 * @param d
 * @param day
 * @return */
 public static Date getDateBefore(Date d,int day){
    Calendar now =Calendar.getInstance();
    now.setTime(d);
    now.set(Calendar.DATE,now.get(Calendar.DATE)-day);
    return now.getTime();
}

/**
 * 得到几天后的时间
 * @param d
 * @param day
 * @return */
  public static Date getDateAfter(Date d,int day){
    Calendar now =Calendar.getInstance();
    now.setTime(d);
    now.set(Calendar.DATE,now.get(Calendar.DATE)+day);
    return now.getTime();
}

/**
 * String   转 Date;
 * @param str
 * @return */

  public static Date StringToDate(String str){

    SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd");//小写的mm表示的是分钟
    Date date= null;
    try {
        date = sdf.parse(str);
    } catch (ParseException e) {
        e.printStackTrace();
    }

    return date;
}

/**
 * String   转 Date;
 * @param str
 * @return */

 public static Date StringToDate(String str){
    //小写mm表示的是分钟
    SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd");
    Date date= null;
    try {
        date = sdf.parse(str);
    } catch (ParseException e) {
        e.printStackTrace();
    }

    return date;
}