如何在不覆盖之前数据的情况下创建多个 java txt 文件？ [复制]

Posted 2023-02-21

【中文标题】如何在不覆盖之前数据的情况下创建多个 java txt 文件？ [复制]

【英文标题】：How to create multiple java txt files without overriding the previous data? [duplicate]

【发布时间】：2012-06-18 20:37:29

【问题描述】：

可能重复：Writing to a file without overwriting or appending

您好，我正在创建一个执行数据并打印到 txt 文件的程序。我遇到的问题是每次运行程序时都会覆盖我以前的 txt 文件。我不想让它覆盖，也不想附加数据。我想每次让它产生一个创建日期或时间时创建一个新的 txt 文件。有人可以帮助我吗？

这是我的代码：

private static PrintWriter outFile;
    /**
     * @param args
     */
    //Main Method
     public static void main(String[] args) throws IOException
        



         //creates the new file to be saved
        outFile = new PrintWriter(new FileWriter("trilogy.txt"));
        //Create a generator object to create random numbers
         Random gen = new Random ();

        //Create a scanner object to scan user input.
         Scanner scan = new Scanner(System.in);

         DateFormat dateFormat = new SimpleDateFormat("yyyy/MM/dd");
         //get current date time with Date()
         Date date = new Date();
         outFile.println(dateFormat.format(date));
         outFile.println();

        //Prompts the user to input how many lock combinations he/she wants generated.
         System.out.print ("Enter quantity: "); 
         int quantity = scan.nextInt();


        int count = 1;
        //Loop - Only numbers 1 - 5 are used
        //       Only five numbers are generated per one lock combination 
         for (int i = 0; i < quantity; i++)
         

                int n1 = gen.nextInt(5)+1;
                int n2 = gen.nextInt(5)+1;
                int n3 = gen.nextInt(5)+1;
                int n4 = gen.nextInt(5)+1;
                int n5 = gen.nextInt(5)+1;


    //While loop making sure that NO numbers are repeated
        while (n2==n1)
         
            n2 = gen.nextInt(5)+1;
         

               while (n3==n2 || n3 == n1 || n3==n4||n3==n5)
               
                   n3 = gen.nextInt(5)+1;
               

                    while (n4 == n3 || n4 == n2 || n4 == n1||n4==n5)
                    
                        n4 = gen.nextInt(5)+1;
                    

                        while (n5== n1 || n5==n2 || n5==n3 || n5==n4)
                        
                            n5 = gen.nextInt(5)+1;
                        

            //If statements that output the random lock combinations in different formats.
                        if (n1==1)
                            outFile.println ("(" + count +") "  +   (n1*10 +n2) +"-"+ (n3*10+n4)+"-"+n5);
                        else if (n2==2)
                            outFile.println ("(" + count +") "  +   n2 + "-" + (n1*10 + n3)+ "-" + (n4*10+ n5));
                        else if (n3==3)
                            outFile.println ("(" + count +") "  +   (n3*10 +n2) +"-"+ n1+ "-" +(n4*10+n5));
                        else if (n4 == 4)
                            outFile.println ("(" + count +") "  +   (n4 +"-"+ (n2*100 +n3*10+n1)+"-"+n5));
                        else
                            outFile.println ("(" + count +") "  +   (n5) +"-"+ (n2) +"-"+ (n3) + "-"+ (n4) +"-" +(n1));

                        count++;

            //Spaces one line in between each lock combination
            outFile.println();

         
         outFile.close();
        

【问题讨论】：

奇怪这个问题是在不到一个小时前被问到的：***.com/questions/11055695/…

这是一个副本，但我更喜欢这个版本而不是原版

【参考方案1】：

您需要更改以下行：

 outFile = new PrintWriter(new FileWriter("trilogy.txt"));

到有时间/日期的东西：

 outFile = new PrintWriter(new FileWriter("trilogy" + DATE_TIME + ".txt"));

【参考方案2】：

尝试改变这个：

        outFile = new PrintWriter(new FileWriter("trilogy.txt"));

为此添加文本：

        outFile = new PrintWriter(new FileWriter("trilogy.txt",true));

:)

【讨论】：

来自 API：docs.oracle.com/javase/1.4.2/docs/api/java/io/FileWriter.html FileWriter(File file, boolean append) 在给定 File 对象的情况下构造 FileWriter 对象。如果第二个参数为真，那么字节将被写入文件的末尾而不是开头。

故事的寓意：总是，总是阅读方法的规范

HI Angel Olle Blazquez 感谢您的反馈。我试图避免它在文件末尾附加和输出。我希望它在每次用户运行程序而不是覆盖时创建一个新的 txt 文件。

试试这个：outFile = new PrintWriter(new FileWriter("trilogy"+new Date()+".txt")); 和评论