java Date的常用處理

/**

• 兩天前日期（yyyy-MM-dd）
• @return */

  public static String getYesterdayDate(){
  Date date=new Date();
  Calendar calendar = new GregorianCalendar();
  calendar.setTime(date);
  calendar.add(Calendar.DATE,-2);
  date=calendar.getTime();
  SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");
  String d = formatter.format(date);
  return d;
  }

/**

• 獲取每月一號(hào)日期（yyyy-MM-dd）
• @return */

  public static String getFirstDayOfMonth(){
   Calendar c = Calendar.getInstance();    
   c.add(Calendar.MONTH, 0);
   c.set(Calendar.DAY_OF_MONTH,1);//設(shè)置為1號(hào),當(dāng)前日期既為本月第一天 
   SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");
   String d = formatter.format(c.getTime());
   return d;
  }

/**

• 獲取某一日期的一周起始日期和結(jié)束日期（即：周一和周日的日期）
• @throws ParseException */

  public static Map<String,String> getWeek(String date) throws ParseException{
  Map<String,String> map=new HashMap<String,String>();
   SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd"); //設(shè)置時(shí)間格式  
   Calendar cal = Calendar.getInstance();  
   Date time=sdf.parse(date);
   cal.setTime(time);  
   System.out.println("要計(jì)算日期為:"+sdf.format(cal.getTime())); //輸出要計(jì)算日期  
   //判斷要計(jì)算的日期是否是周日，如果是則減一天計(jì)算周六的，否則會(huì)出問(wèn)題，計(jì)算到下一周去了  
  int dayWeek = cal.get(Calendar.DAY_OF_WEEK);//獲得當(dāng)前日期是一個(gè)星期的第幾天  
  if(1 == dayWeek) {  
       cal.add(Calendar.DAY_OF_MONTH, -1);  
    }  
  cal.setFirstDayOfWeek(Calendar.MONDAY);//設(shè)置一個(gè)星期的第一天，按中國(guó)的習(xí)慣一個(gè)星期的第一天是星期一  
  int day = cal.get(Calendar.DAY_OF_WEEK);//獲得當(dāng)前日期是一個(gè)星期的第幾天  
  cal.add(Calendar.DATE, cal.getFirstDayOfWeek()-day);//根據(jù)日歷的規(guī)則，給當(dāng)前日期減去星期幾與一個(gè)星期第一天的差值   
  String startDay=sdf.format(cal.getTime());
  cal.add(Calendar.DATE, 6);
  String endDay=sdf.format(cal.getTime());
  map.put("startDay", startDay);
  map.put("endDay", endDay);
  System.out.println(map);
  return map;
  }
  public static void main(String [] args) throws ParseException{
  getWeek("2016-04-24");
  }

  
  /**

• 獲取某一日期是周幾
• @throws ParseException */

  public static String getWeekOfDate(Date dt) throws ParseException {
      String[] weekDays = {"Sun","Mon", "Tue", "Wed", "Thu", "Fri", "Sat"};
      Calendar cal = Calendar.getInstance();
      cal.setTime(dt);
      int w = cal.get(Calendar.DAY_OF_WEEK)-1;
      if (w < 0)
          w = 0;
      return weekDays[w];
  }

  /**

  • 將date（2016-12-02）轉(zhuǎn)換為（12.2）
  • @throws ParseException */

    public static String getDay(String date) throws ParseException{
    String s=Integer.parseInt(date.substring(5,7))+"."+Integer.parseInt(date.substring(8,10));
    return s;
    }

/**

• 將小數(shù)轉(zhuǎn)為百分?jǐn)?shù)(99.2%)
• @throws ParseException */

  public static String getProportion(int a,int b){
    String pro="";
    if(a!=0&&b!=0){
        double percent = (double)a/b;
        //獲取格式化對(duì)象
        NumberFormat nt = NumberFormat.getPercentInstance();
        //設(shè)置百分?jǐn)?shù)精確度1即保留兩位小數(shù)
        nt.setMinimumFractionDigits(1);
        //最后格式化并輸出
        pro=nt.format(percent);
    }
      return pro;
  }

  /**

• 將小數(shù)轉(zhuǎn)為百分?jǐn)?shù)(+/-7.5%)
• @throws ParseException */

  public static String getProportionSign(int a,int b){
    String pro="";
    if(a!=0&&b!=0){
      double percent = (double)a/b;
     //獲取格式化對(duì)象
      NumberFormat nt = NumberFormat.getPercentInstance();
     //設(shè)置百分?jǐn)?shù)精確度1即保留兩位小數(shù)
      nt.setMinimumFractionDigits(1);
     //最后格式化并輸出
      if(percent>1){
          pro="+"+nt.format(percent-1);
      }else{
          pro=nt.format(percent-1);
      }
    }
      return pro;
  }