Question

我编写了一个程序，该程序应该从现有文件中获取一个值，将该值添加一个，删除该文件，创建该文件的新实例，并将新值写入该文件的新实例

public static void main(String[] args) throws InterruptedException, IOException {

    //initialize newFile and writer
    File newFile = new File("C:\\Users\\boung\\Desktop\\python\\daysSince.txt");
    FileWriter writer = new FileWriter("C:\\Users\\boung\\Desktop\\python\\daysSince.txt", true);

    //if newFile doesn't exist or of newFile doesn't contain any content, create newFile and write "1" to newFile
    if(newFile.length() == 0) {

        System.out.println("empty");
        writer.write("1");
        writer.write("\r\n");
        writer.close();

    } else {

        //get contents of newFile
        StringBuilder contentBuilder01 = new StringBuilder();                       
        try (Stream<String> stream = Files.lines( Paths.get("C:\\Users\\boung\\Desktop\\python\\daysSince.txt"), StandardCharsets.UTF_8)) {

                stream.forEach(s -> contentBuilder01.append(s).append("\n"));

            } catch (IOException e) {

                e.printStackTrace();

            }

        //convert content to integer
        String content = contentBuilder01.toString();
        content = content.replaceAll("\\D+", "");
        int value = Integer.parseInt(content);
        System.out.println(value);

        //add 1 to the value that was returned from getting the contents of newFile and assign it to newValue
        int newValue = value + 1;

        //delete newFile
        newFile.delete();

        //create new instance of newFile to prepare for next execution
        if(newFile.length() == 0) { 
        newFile = new File("C:\\Users\\boung\\Desktop\\python\\daysSince.txt");
        }

        FileWriter writer1 = new FileWriter("C:\\Users\\boung\\Desktop\\python\\daysSince.txt", true);          

        //write newValue to new instance of newFile
        writer1.write(newValue);
        System.out.println("printed " + newValue);
        writer1.write("\r\n");
        writer1.close();
    }



}

此区域出现了问题

        writer1.write(newValue);
        System.out.println("printed " + newValue);
        writer1.write("\r\n");
        writer1.close();

假设newFile不存在，在两次运行程序后，预期输出将如下所示

2

但这是我得到的输出

1

但是在这里，如果文件为空或不存在，程序将1写入文件没有问题

    System.out.println("empty");
    writer.write("1");
    writer.write("\r\n");
    writer.close();

我认为我在程序逻辑上犯了一个错误，有人可以帮忙吗？

Answer 1

我相信您的程序有两个问题：

newFile.delete();不执行任何操作，因为writer仍处于打开状态。您需要先通过执行writer关闭writer.close();。
writer1.write(newValue);将newValue写为int。这意味着它实际上是采用代表该数字的所有二进制数字并将它们直接写入文件中。相反，您想将newValue写为String，它将在文本中产生该数字，以便您可以读取它。因此，您想改用writer1.write(Integer.toString(newValue));。

Answer 2

newFile.delete();是不必要的，您无需删除文件即可再次写入。以下代码示例适用于我并正确输出。

    StringBuilder contentBuilder01 = new StringBuilder();
    try (Stream<String> stream = Files.lines( Paths.get(fileName), StandardCharsets.UTF_8)) {
        stream.forEach(s -> contentBuilder01.append(s).append("\n"));
    } catch (IOException e) {
        e.printStackTrace();
    }
    FileWriter writer = new FileWriter(fileName);
    writer.write(Integer.toString(Integer.parseInt(contentBuilder01.toString().trim()) + 1));
    writer.close();

FileWriter未写入文件

2 个答案: