Java 各種時間上的操作範例

分享一些在專案中用到JAVA與日期相關的操作,包括:

  • 取得目前的年、月、日
  • 判斷兩個日期的大小
  • 計算兩個日期的差距
  • 取得昨天的日期
  • 取得上個月的開始與結束日
package CDIT.stanley;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;
import java.util.Calendar;

public class dateOperation {
	
	public static int differentDays(Date date1,Date date2){
        Calendar cal1 = Calendar.getInstance();
        cal1.setTime(date1);
        
        Calendar cal2 = Calendar.getInstance();
        cal2.setTime(date2);
        int day1= cal1.get(Calendar.DAY_OF_YEAR);
        int day2 = cal2.get(Calendar.DAY_OF_YEAR);
        
        int year1 = cal1.get(Calendar.YEAR);
        int year2 = cal2.get(Calendar.YEAR);
        if(year1 != year2){
            int timeDistance = 0 ;
            for(int i = year1 ; i < year2 ; i ++){
                if(i%4==0 && i%100!=0 || i%400==0){
                    timeDistance += 366;
                }
                else{
                    timeDistance += 365;
                }
            }
            return timeDistance + (day2-day1) ;
        }
        else{
            return day2-day1;
        }
    }
	
	public static Date getFirstMonthDay(Calendar calendar) {
		calendar.set(Calendar.DATE, calendar.getActualMinimum(Calendar.DATE));
		return calendar.getTime();
	}

	public static Date getLastMonthDay(Calendar calendar) {
		calendar.set(Calendar.DATE, calendar.getActualMaximum(Calendar.DATE));
		return calendar.getTime();
	}
	
    public static void main(String[] args) throws ParseException {
    	
    	//取得目前的年、月、日
		Calendar calendar = Calendar.getInstance();	
		System.out.println("今天是" + calendar.get(Calendar.YEAR) + "年" + (calendar.get(Calendar.MONTH) + 1) + "月" + calendar.get(Calendar.DAY_OF_MONTH) + "日");
		System.out.println("==================================================");
    	//輸出:今天是2017年8月24日
		
		//判斷兩個日期的大小
    	SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd", Locale.TAIWAN);
    	Date date1 = sdf.parse("2017-08-23");
    	Date date2 = sdf.parse("2016-09-22");
		System.out.println("Date1 < Date2 : " + date1.before(date2));
		System.out.println("Date1 > Date2 : " + date1.after(date2));
		System.out.println("==================================================");
		//輸出:Date1 < Date2 : false、Date1 > Date2 : true
		
		//計算兩個日期的差距
		System.out.println("Date1 & Date2 差距 : " + differentDays(date1 , date2) + "天");
		System.out.println("==================================================");
		//輸出:Date1 & Date2 差距 : 31天
		
		//取得昨天的日期
		calendar = Calendar.getInstance();
		calendar.add(Calendar.DATE, -1);
		String  yestedayDate = sdf.format(calendar.getTime());
		System.out.println("昨天是" + yestedayDate);
		System.out.println("==================================================");
		//輸出:昨天是2017-08-23
		
		//取得上個月的開始與結束日
		calendar = Calendar.getInstance();
		calendar.add(Calendar.MONTH,-1);
		String monthDayFirst = sdf.format(getFirstMonthDay(calendar));
		String monthDayLast = sdf.format(getLastMonthDay(calendar));
		System.out.println("上個月的第一天是" + monthDayFirst);
		System.out.println("上個月的最後一天是" + monthDayLast);
		System.out.println("==================================================");
		//輸出:上個月的第一天是2017-07-01、上個月的最後一天是2017-07-31
    }
}

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