FileWriter未写入文件

Question

我已经编写了一个程序，该程序应该从现有文件中获取一个值，将该值添加到该值上，删除该文件，创建该文件的一个新实例，并将新的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();
    }



}       

问题发生在此区域。

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

假设newFile不存在，在运行该程序两次之后，预期的输出将如下所示

2

但这是我得到的输出

1

但在这里，如果文件为空或不存在，则程序可以将1写入文件

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

我想我在程序的逻辑上犯了一个错误，有谁能帮助我吗？

Answer 1

我认为你的程序有两个问题：

因为writer仍处于打开状态，所以

1. newFile.delete();不执行任何操作。您需要首先通过执行writer.close();.
2. writer1.write(newValue); writes newValue as an int来关闭writer。这意味着它直接获取表示该数字的所有二进制数，并将它们直接写入文件。相反，您希望将newValue编写为String，这将以文本形式生成该数字，以便您可以阅读它。因此，您希望使用writer1.write(Integer.toString(newValue));。

Answer 2

newFile.delete();是不必要的，您不需要删除该文件即可再次写入。下面的代码示例适用于我，并且输出正确。

    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();