为什么我的 fileOutputstream 忽略附加“true”旗帜？

发布于 2025-01-17 03:31:41 字数 1015 浏览 0 评论 0原文

我正在尝试包装 FileinputStream 并在包装类“Amigo”中更改 Parent 的 close 方法。正如您在代码中看到的，我使用默认的 FileInputStream 对象在使用 .close() 方法的情况下在文件末尾写入一些数据。但是，尽管我在 fileOutputStream 字段中使用“append”到“true”标志，但我的程序仍然会覆盖文件中的数据。为什么会出现这种情况呢？

public class AmigoOutputStream extends FileOutputStream{
public static String fileName = "C:\\Users\\Егор\\IdeaProjects\\JavaRushTasks\\2.JavaCore\\src\\com\\javarush\\task\\task18\\task1813\\r.txt";
private FileOutputStream fileOutputStream = new FileOutputStream(fileName,true);
private static final String JAVA_RUSH = "JavaRush © All rights reserved.";


public AmigoOutputStream(FileOutputStream name) throws FileNotFoundException {
    super(String.valueOf(name),true);
}

public static void main(String[] args) throws IOException {
    new AmigoOutputStream(new FileOutputStream(fileName)).close();
}

@Override
public void close() throws IOException {
    fileOutputStream.flush();
    fileOutputStream.write(JAVA_RUSH.getBytes());
    fileOutputStream.close();
}

}

原文

I m trying to wrap FileinputStream and change close method of Parent in my wrapper class "Amigo". As u can see in code, i use default FileInputStream object to write some data in end of file in case of using .close() method. But, despite that i use "append" to "true" flag in the fileOutputStream field, my programm is still overwrites data in file. Why is this happens?

public class AmigoOutputStream extends FileOutputStream{
public static String fileName = "C:\\Users\\Егор\\IdeaProjects\\JavaRushTasks\\2.JavaCore\\src\\com\\javarush\\task\\task18\\task1813\\r.txt";
private FileOutputStream fileOutputStream = new FileOutputStream(fileName,true);
private static final String JAVA_RUSH = "JavaRush © All rights reserved.";


public AmigoOutputStream(FileOutputStream name) throws FileNotFoundException {
    super(String.valueOf(name),true);
}

public static void main(String[] args) throws IOException {
    new AmigoOutputStream(new FileOutputStream(fileName)).close();
}

@Override
public void close() throws IOException {
    fileOutputStream.flush();
    fileOutputStream.write(JAVA_RUSH.getBytes());
    fileOutputStream.close();
}

}

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淡水深流 2025-01-24 03:31:41

main 内的 new FileOutputStream(fileName) 行将擦除文件，并且该行在 new FileOutputStream(fileName,true) 之前运行，该文件位于班级。

您还创建了一个具有不寻常名称的新文件 - 设置为 String.valueOf(name)。您可能需要这样的东西，它允许调用者指定文件，并意味着 AmigoOutputStream 始终向某个文件发送额外的字节：

public class AmigoOutputStream extends FileOutputStream{
    private static final String JAVA_RUSH = "JavaRush © All rights reserved.";

    public AmigoOutputStream(String name) throws FileNotFoundException {
        super(name,true);
    }

    public static void main(String[] args) throws IOException {
        try(OutputStream os = new AmigoOutputStream("r.txt")) {
        }
    }

    @Override
    public void close() throws IOException {
        write(JAVA_RUSH.getBytes());
        super.close();
    }
}

The line with new FileOutputStream(fileName) inside main will wipe the file and that runs before new FileOutputStream(fileName,true) which is inside the class.

You are also creating a new file which has an unusual name - set to String.valueOf(name). You may want something like this which allows caller to specify the file and means AmigoOutputStream always sends extra bytes to some file:

public class AmigoOutputStream extends FileOutputStream{
    private static final String JAVA_RUSH = "JavaRush © All rights reserved.";

    public AmigoOutputStream(String name) throws FileNotFoundException {
        super(name,true);
    }

    public static void main(String[] args) throws IOException {
        try(OutputStream os = new AmigoOutputStream("r.txt")) {
        }
    }

    @Override
    public void close() throws IOException {
        write(JAVA_RUSH.getBytes());
        super.close();
    }
}

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