如何根據用戶輸入創建輸入和輸出文件？

Question

輸入文件DATA1.txt將包含7行，每行都有一個描述每種類型糖果數量的正整數。輸出文件OUT1.txt將包含與輸入的數字相同的星號。 即： 輸入DATA1.TXT會顯示：

12 
8 
10 
5 
20 
3 
7 

輸出OUT1.txt會顯示：

12: ************ 
8: ******** 
10: ********** 
5: ***** 
20: ******************** 
3: *** 
7: ******* 

當我運行我的代碼，它僅創建一個文件，該文件是OUT1.txt但它有數字而不是星星。我怎麼會有一個DATA1.txt呢？我不太明白這一點，因爲我沒有了解輸入或輸出文件。任何幫助將不勝感激。我會在我的代碼中修改什麼？

import javax.swing.*; 
import java.io.*; 
import java.io.File; 
import java.io.FileNotFoundException; 
import java.util.ArrayList; 
import java.util.Collections; 
import java.util.Scanner; 
class CandyLand{ 
    public static void main(String str[]){ 
     int num1,num2,num3,num4,num5,num6,num7; 

     String input1 = JOptionPane.showInputDialog("Please, enter the number of candies in the first pile"); 
     num1 = Integer.parseInt(input1); 
     String input2 = JOptionPane.showInputDialog("Please, enter the number of candies in the second pile"); 
     num2 = Integer.parseInt(input2); 
     String input3 = JOptionPane.showInputDialog("Please, enter the number of candies in the third pile"); 
     num3 = Integer.parseInt(input3); 
     String input4 = JOptionPane.showInputDialog("Please, enter the number of candies in the fourth pile"); 
     num4 = Integer.parseInt(input4); 
     String input5 = JOptionPane.showInputDialog("Please, enter the number of candies in the fifth pile"); 
     num5 = Integer.parseInt(input5); 
     String input6 = JOptionPane.showInputDialog("Please, enter the number of candies in the sixth pile"); 
     num6 = Integer.parseInt(input6); 
     String input7 = JOptionPane.showInputDialog("Please, enter the number of candies in the seventh pile"); 
     num7 = Integer.parseInt(input7); 

     String fileName = JOptionPane.showInputDialog("Please, enter the name of the file"); 
     try{ 

      DataOutput f = new DataOutputStream(new FileOutputStream(fileName +".txt")); 
      f.writeBytes(String.valueOf(num1)); 
      f.writeBytes("\r\n"); 
      f.writeBytes(String.valueOf(num2)); 
      f.writeBytes("\r\n"); 
      f.writeBytes(String.valueOf(num3)); 
      f.writeBytes("\r\n"); 
      f.writeBytes(String.valueOf(num4)); 
      f.writeBytes("\r\n"); 
      f.writeBytes(String.valueOf(num5)); 
      f.writeBytes("\r\n"); 
      f.writeBytes(String.valueOf(num6)); 
      f.writeBytes("\r\n"); 
      f.writeBytes(String.valueOf(num7)); 
     } 
     catch(Exception e){ 
      String msg = e.toString(); 
      System.out.println(msg); 
     } 

     Scanner file = null; 
     ArrayList<Integer> list = new ArrayList<Integer>(); 

     try { 
      file = new Scanner(new File("OUT1.txt")); 
     } catch (FileNotFoundException e) { 
      e.printStackTrace(); 
     } 

     while(file.hasNext()){ 
      if (file.hasNextInt()) list.add(file.nextInt()); 
      else file.next(); 
     } 
     for (Integer j: list){ 
      System.out.print(j + ": "); 
      for(int i=1; i<=j; i++){ 
       System.out.print("* "); 
      } 
      System.out.println(""); 
     } 
    } 
} 

Answer 1

您是否預先創建了任何文件？如果我沒有預先創建文件的情況下運行這個，我輸入七個數字和文件名「test」。該程序停止在：

java.io.FileNotFoundException：OUT1.txt（系統找不到指定的文件）

我現在看到的test.txt與裏面的7號創建。這是第一次運行，沒有我之前手動創建的文件。 OUT1.txt未創建。

如何在OUT1.txt文件不存在的情況下運行while循環？

while(file.hasNext()){ 
    if (file.hasNextInt()) 
     list.add(file.nextInt()); 
    else file.next(); 
} 

我正在修復當我完成後我將編輯的程序，但我希望你先理解。

代碼：（我評論的變化）

import javax.swing.*; 
import java.io.*; 
import java.io.File; 
import java.io.FileNotFoundException; 
import java.util.ArrayList; 
import java.util.Collections; 
import java.util.Scanner; 

public class CandyLand{ 
    public static void main(String str[]){ 
     int num1,num2,num3,num4,num5,num6,num7; 

     String input1 = JOptionPane.showInputDialog("Please, enter the number of candies in the first pile"); 
     num1 = Integer.parseInt(input1); 
     String input2 = JOptionPane.showInputDialog("Please, enter the number of candies in the second pile"); 
     num2 = Integer.parseInt(input2); 
     String input3 = JOptionPane.showInputDialog("Please, enter the number of candies in the third pile"); 
     num3 = Integer.parseInt(input3); 
     String input4 = JOptionPane.showInputDialog("Please, enter the number of candies in the fourth pile"); 
     num4 = Integer.parseInt(input4); 
     String input5 = JOptionPane.showInputDialog("Please, enter the number of candies in the fifth pile"); 
     num5 = Integer.parseInt(input5); 
     String input6 = JOptionPane.showInputDialog("Please, enter the number of candies in the sixth pile"); 
     num6 = Integer.parseInt(input6); 
     String input7 = JOptionPane.showInputDialog("Please, enter the number of candies in the seventh pile"); 
     num7 = Integer.parseInt(input7); 

     String fileName = JOptionPane.showInputDialog("Please, enter the name of the file"); 
     try{ 
     DataOutput f = new DataOutputStream(new FileOutputStream(fileName + ".txt")); 
     f.writeBytes(String.valueOf(num1)); 
     f.writeBytes("\r\n"); 
     f.writeBytes(String.valueOf(num2)); 
     f.writeBytes("\r\n"); 
     f.writeBytes(String.valueOf(num3)); 
     f.writeBytes("\r\n"); 
     f.writeBytes(String.valueOf(num4)); 
     f.writeBytes("\r\n"); 
     f.writeBytes(String.valueOf(num5)); 
     f.writeBytes("\r\n"); 
     f.writeBytes(String.valueOf(num6)); 
     f.writeBytes("\r\n"); 
     f.writeBytes(String.valueOf(num7)); 
     } 
     catch(Exception e){ 
     String msg = e.toString(); 
     System.out.println(msg); 
     } 

     Scanner file = null; 
     ArrayList<Integer> list = new ArrayList<Integer>(); 

     try { 
     //You should be reading from the first file you created, not OUT1.txt 
     file = new Scanner(new File(fileName + ".txt")); 
     } 
     catch (FileNotFoundException e) { 
     e.printStackTrace(); 
     } 

     while(file.hasNext()){ 
     if (file.hasNextInt()) 
      list.add(file.nextInt()); 
     else file.next(); 
     } 
     try { 
     //Instead using System.out.println, use DataOutput like you were using before 
     DataOutput f2 = new DataOutputStream(new FileOutputStream("OUT1.txt")); 
     for (Integer j: list){ 
      f2.writeBytes(j + ": "); 
      for(int i=1; i<=j; i++){ 
       f2.writeBytes("* "); 
      } 
      f2.writeBytes("\r\n"); 
     } 
     } 
     catch(Exception e){ 
     e.printStackTrace(); 
     } 
    } 
}