Java 中的 FileWriter 与 FileOutputStream

FileWriter vs FileOutputStream in Java

提问by Jon Skeet

I'm little confused about FileWriterand FileOutputStream. As I see source code of FileWriterthere are just 4 constructors and each constructor is calling FileOutputStream's constructor.

我对FileWriter和有点困惑FileOutputStream。正如我看到的 FileWriter 的源代码只有 4 个构造函数，每个构造函数都在调用FileOutputStream的构造函数。

public FileWriter(String fileName) throws IOException {
       super(new FileOutputStream(fileName));
}
public FileWriter(String fileName, boolean append) throws IOException {
        super(new FileOutputStream(fileName, append));
}
public FileWriter(File file) throws IOException {
        super(new FileOutputStream(file));
}
public FileWriter(File file, boolean append) throws IOException {
        super(new FileOutputStream(file, append));
}
public FileWriter(FileDescriptor fd) {
        super(new FileOutputStream(fd));
}

After searching difference between them I found mentioned here.

在搜索它们之间的差异后，我发现这里提到了。

FileOutputStream is meant for writing streams of raw bytes such as image data. For writing streams of characters, consider using FileWriter.

FileOutputStream 用于写入原始字节流，例如图像数据。要写入字符流，请考虑使用 FileWriter。

How FileWritercan make difference? Even it still calling FileOutputStream's constructor without any changing.

怎样FileWriter才能有所作为？即使它仍然调用FileOutputStream的构造函数而没有任何改变。

回答by Jon Skeet

FileWriteris a Writer. It's about writing text- and it happens to be writing it to a file. It does that by holding a reference to a FileOutputStream, which is created in the FileWriterconstructor and passed to the superclass constructor.

FileWriter是一个Writer。这是关于编写文本- 它恰好是将其写入文件。它通过持有对 a 的引用来实现FileOutputStream，该引用在FileWriter构造函数中创建并传递给超类构造函数。

FileOutputStreamis an OutputStream. It's about writing binary data. If you want to write text to it, you need something to convert that text to binary data - and that's exactly what FileWriterdoes. Personally I prefer to use FileOutputStreamwrapped in an OutputStreamWriterby meto allow me to specify the character encoding (as FileWriteralways uses the platform default encoding, annoyingly).

FileOutputStream是一个OutputStream。这是关于写入二进制数据。如果你想向它写入文本，你需要一些东西来将该文本转换为二进制数据——这正是FileWriter它的作用。就我个人而言，我更喜欢使用FileOutputStream包装在一个OutputStreamWriter由我来允许我指定字符编码（因为FileWriter总是使用平台默认编码，很烦人）。

Basically, think of FileWriteris a simple way of letting you write:

基本上，think ofFileWriter是一种让您编写的简单方法：

Writer writer = new FileWriter("test.txt");

instead of

代替

Writer writer = new OutputStreamWriter(new FileOutputStream("test.txt"));

Except I'd normally recommend using the overload of the OutputStreamWriterconstructor that accepts a Charset.

除非我通常建议使用OutputStreamWriter接受 a的构造函数的重载Charset。

回答by Willy du Preez

A FileOutputStreamwrites bytes directly. A FileWriterencapsulates a FileOutputStream(by creating it in the FileWriterconstructor as in your question) and provides convenience methods to write characters and Strings.

AFileOutputStream直接写入字节。AFileWriter封装了 a FileOutputStream（通过在FileWriter构造函数中创建它，如您的问题一样）并提供方便的方法来编写字符和字符串。

回答by Scion11

FileOutputStreamis to write primitive types of data, like int, while FileWriteris to write character-oriented data.

FileOutputStream是编写原始类型的数据，例如int，而FileWriter编写面向字符的数据。

FileOutputStreamdoes not come with methods to deal with strings. If you want to use FileOutputStreamto write a string to a file, you have to go like:

FileOutputStream没有附带处理字符串的方法。如果要使用FileOutputStream将字符串写入文件，则必须执行以下操作：

FileOutputStream fos=new FileOutputStream();
String str="Hello";
byte b[]=str.getBytes();
fos.write(b);
fos.close();

In Filewriterthere is no conversion between string and byte array. You could simply use:

在Filewriter字符串和字节数组之间没有转换。你可以简单地使用：

FileWriter fr=new FileWriter("C:\");
fr.write("Hello");
fr.close();

Do not forget to throw any exceptions if needed.

如果需要，不要忘记抛出任何异常。