如何在字符串數據類型的jtextfield中給出的日期添加天數

Question

美好的一天。 我只想問一個給定的日期添加日期。 我有一個jtexfield（txtStart）和另一個jtexfield（txtExpiry）。 我需要在txtStart中的日期後102天后在txtExpiry中顯示日期。 我正在使用KEYRELEASED事件。在我輸入txtStart之後，額外102天的日期將出現在txtExpiry中。

這是我的代碼，但它仍然是錯誤的。

private void txtStartKeyReleased(java.awt.event.KeyEvent evt) { 
// TODO add your handling code here: 
    // set calendar to 1 Jan 2007 
    int a = Integer.parseInt(txtStart.getText());  
    Calendar calendar = new GregorianCalendar(a,a,a); 

    calendar.add(Calendar.DAY_OF_MONTH,102); 
    PrintCalendar(calendar); 
    } 

    private void PrintCalendar(Calendar calendar){ 
     // define output format and print 
     SimpleDateFormat sdf = new SimpleDateFormat("yyyy-mm-dd");   
     String date = sdf.format(calendar.getTime()); 
     long add = Date.parse(date); 
     txtExpiry.setText(add); -----> this part here also has an error. 
    } 

我的代碼仍然不會在txtExpiry中生成日期。在此先感謝

這裏是接受幫助後，正確的代碼：

private void txtStartKeyReleased(java.awt.event.KeyEvent evt) { 
     try {  

     Date date1; 
     date1 = new SimpleDateFormat("yyyy-MM-dd").parse(txtStart.getText()); 
     System.out.println(date1); 

     SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");  
     Calendar cal = Calendar.getInstance(); 
         cal.setTime(date1); 
         cal.add(Calendar.DATE, 102); 
         String expDateString = sdf.format(cal.getTime()); 
         txtExpiry.setText(expDateString); 
    }catch (ParseException ex) { 
     Logger.getLogger(ClientInfo.class.getName()).log(Level.SEVERE, null, ex); 
    } 
} 

Answer 1

使用

yyyy-MM-dd 

注：資本MM

參見：SimpleDateFormat

現在，一旦你有數據E時，你可以使用Calendar做天算術

Calendar cal = Calendar.getInstance(); 
cal.setTime(parsedDate); 
cal.add(Calendar.DATE, 102); 
String expDateString = dateFormatter.format(cal.getTime()); 

Answer 2

一旦你有了正確的format，你可以使用JodaTime。您可以直接解析使用JodaTime的String值，但既然你已經這樣做了，我不打擾...

Date date = ...; 
DateTime dt = new DateTime(date); 
dt = dt.plusDays(102); 
date = dt.toDate(); 

Answer 3

import java.util.*; 
class ISCprac2009q01{ 
public static void main(String args[]) 
throws InputMismatchException{ 

Scanner scan=new Scanner(System.in); 
System.out.println("ENTER DAY NUMER(>=1 AND 
<=366) : "); 
int day_number=scan.nextInt(); 
System.out.println("ENTER YEAR(4 DIGIT) : "); 
int year=scan.nextInt(); 
System.out.println("ENTER DATE AFTER(N)(>=1 AND 
<=100) : "); 
int n=scan.nextInt(); 

if(day_number<1 || day_number>366) 
System.out.println("INVALID DAY NUMBER."); 
else if(year<1000 || year >9999) 
System.out.println("INVALID YEAR"); 
else if(n<1 || n>100) 
System.out.println("INVALID DATE AFTER VALUE."); 
else{ 
//INITIALIZE MONTH NAMES AND NUMBER OF DAYS IN EACH MONTH 
    String month_names[]={"JANUARY", "FEBRUARY","MARCH", 
     "APRIL","MAY","JUNE","JULY","AUGUST","SEPTEMBER", 
     "OCTOBER","NOVERMBER","DECEMBER"}; 
    int month_days[]={31,28,31,30,31,30,31,31,30,31,30,31}; 
    int i, day, month,day_after; 
    String suffix; 

    //IF IT IS A LEAP YEAR FEBRURAY SHOULD HAVE 29 DAYS 
    if(year%400==0 || (year%100!=0 && year%4==0)) 
     month_days[1]=29; 

     i=0; 
    //FIND THE DATE CORRESPONDING TO THE DAY NUMBER 
     day=day_number; 
     while(day>month_days[i]) 
     { 
      day-=month_days[i]; 
      i++; 
     } 
     month=i; 
     //ADD SUFFIX AS PER THE DAY 
     if(day%10==1 && day/10!=1) 
      suffix="ST"; 
     else if(day%10==2 && day/10!=1) 
      suffix="ND"; 
     else if(day%10==3 && day/10!=1) 
      suffix="RD"; 
     else 
      suffix="TH"; 
     System.out.println("OUTPUT:"); 
     //FIRST PART OF THE OUTPUT 
     System.out.println(day+suffix+" "+ 
     month_names[month]+" "+year); 

     //TO CALCULATE DATE AFTER N DAYS 
     day_after=day_number+n; 
     i=0; 
     while(day_after>month_days[i]) 
     { 
      day_after-=month_days[i]; 
      i++; 
      if(i==12){ 
      i=0; 
      year++; 
      if(year%400==0 || (year%100!=0 && year%4==0)) 
       month_days[1]=29; 
      } 
     } 
     day=day_after; 
     month=i; 
     //ADD SUFFIX AS PER THE DAY 
     if(day%10==1 && day/10!=1) 
      suffix="ST"; 
     else if(day%10==2 && day/10!=1) 
      suffix="ND"; 
     else if(day%10==3 && day/10!=1) 
      suffix="RD"; 
     else 
      suffix="TH"; 
     //SECOND PART OF THE OUTPUT 
     System.out.println(day+suffix+" "+ 
     month_names[month]+" "+year); 
} 
} 
}