java获取当前日期的前一天日期与字符串日期之间的转换

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这几天一直在处理Java的日期问题，通常需要按要求生成日期的话，通常会用到util包中的Calendar类，再用Calendar的getTime()方法生成对应的Date，最后用SimpleDateFormat输出。

1.获取当期日期、年份、月份

import java.util.Calendar;

public class Main {
  public static void main(String[] args) {
    Calendar now = Calendar.getInstance();
    System.out.println("Current Year is : " + now.get(Calendar.YEAR));
    // month start from 0 to 11
    System.out.println("Current Month is : " + (now.get(Calendar.MONTH) + 1));
    System.out.println("Current Date is : " + now.get(Calendar.DATE));
  }
}

2.获取前一天、前一个月的日期

Calendar calendar = Calendar.getInstance();//此时打印它获取的是系统当前时间 calendar.add(Calendar.DATE, -1); //得到前一天

String yestedayDate

= new SimpleDateFormat("yyyy-MM-dd").format(cal.getTime());

例:

public static Date getNextDay(Date date) {Calendar calendar = Calendar.getInstance();calendar.setTime(date);calendar.add(Calendar.DAY_OF_MONTH, -1);date = calendar.getTime();return date;}

再例: 精确到时分秒

private Timestamp getPreviDay() throws ParseException{
       Calendar calendar = Calendar.getInstance();
       calendar.setTime(new Date());
       calendar.add(Calendar.DAY_OF_MONTH, -1);
       String date = new SimpleDateFormat("yyyy-MM-dd").format(calendar.getTime());

       Date d = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS").parse(date+" 23:59:59.000");

       Timestamp ta = new Timestamp(d.getTime());
       return ta;
   }

calendar.add(Calendar.MONTH, -1); //得到前一个月 int year = calendar.get(Calendar.YEAR);

int month = calendar.get(Calendar.MONTH)+1; //输出前一月的时候要记得加1

3.字符串转为日期格式

String date ="2010-02-01 23:59:59";

SimpleDateFormat sf =new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");

try {

Date d = sf.parse(date);

System.out.println(sf.format(d));

}catch (ParseException e) {

e.printStackTrace();

}

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