FileWriter 不写入文件答案

【问题标题】：FileWriter not writing to fileFileWriter 不写入文件
【发布时间】：2020-09-29 05:33:42
【问题描述】：

我编写了一个程序，它应该从现有文件中获取一个值，向该值添加一个，删除文件，创建文件的新实例，并将新值写入文件的新实例.

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();
    }



}

这个问题正在发生

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

假设newFile 不存在，在运行程序两次后，预期的输出将如下所示

2

但这是我得到的输出

1

但是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();

我认为我在程序的逻辑上犯了一个错误，有人可以帮忙吗？

【问题讨论】：

标签： java filewriter file-writing

【解决方案1】：

我相信你的程序有两个问题：

newFile.delete(); 什么都不做，因为 writer 仍然打开。您需要先关闭writer，方法是执行writer.close();。
writer1.write(newValue); 将newValue 写入int。这意味着它从字面上获取代表该数字的所有二进制数字并将它们直接写入文件。相反，您想将newValue 写为String，这将在文本中生成该数字，以便您阅读。所以你想改用writer1.write(Integer.toString(newValue));。

【讨论】：

【解决方案2】：

newFile.delete(); 是不必要的，你不需要删除文件来再次写入它。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();

【讨论】：