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I was surprised to find today that I couldn't track down any simple way to write the contents of an InputStream to an OutputStream in Java. 今天我很惊讶地发现，我无法找到将InputStream的内容写入Java中的OutputStream任何简单方法。 Obviously, the byte buffer code isn't difficult to write, but I suspect I'm just missing something which would make my life easier (and the code clearer). 显然，字节缓冲区代码并不难写，但我怀疑我只是遗漏了一些会让我的生活更轻松（代码更清晰）的东西。

So, given an InputStream in and an OutputStream out , is there a simpler way to write the following? 因此，给定InputStream in和OutputStream out ，有没有写以下简单的方法？

byte[] buffer = new byte[1024];int len = in.read(buffer);while (len != -1) {    out.write(buffer, 0, len);    len = in.read(buffer);}

#1楼

参考：

#2楼

Another possible candidate are the Guava I/O utilities: 另一个可能的候选者是Guava I / O实用程序：

I thought I'd use these since Guava is already immensely useful in my project, rather than adding yet another library for one function. 我以为我会使用这些，因为Guava在我的项目中已经非常有用，而不是为一个函数添加另一个库。

#3楼

I think it's better to use a large buffer, because most of the files are greater than 1024 bytes. 我认为最好使用大缓冲区，因为大多数文件大于1024字节。 Also it's a good practice to check the number of read bytes to be positive. 另外，最好将读取的字节数检查为正数。

byte[] buffer = new byte[4096];int n;while ((n = in.read(buffer)) > 0) {    out.write(buffer, 0, n);}out.close();

#4楼

Simple Function 简单的功能

If you only need this for writing an InputStream to a File then you can use this simple function: 如果您只需要这个来将InputStream写入File那么您可以使用这个简单的函数：

private void copyInputStreamToFile( InputStream in, File file ) {    try {        OutputStream out = new FileOutputStream(file);        byte[] buf = new byte[1024];        int len;        while((len=in.read(buf))>0){            out.write(buf,0,len);        }        out.close();        in.close();    } catch (Exception e) {        e.printStackTrace();    }}

#5楼

If you are using Java 7, (in the standard library) is the best approach: 如果您使用的是Java 7，则 （在标准库中）是最佳方法：

/* You can get Path from file also: file.toPath() */Files.copy(InputStream in, Path target)Files.copy(Path source, OutputStream out)

Edit: Of course it's just useful when you create one of InputStream or OutputStream from file. 编辑：当然，从文件创建一个InputStream或OutputStream时它非常有用。 Use file.toPath() to get path from file. 使用file.toPath()从文件中获取路径。

To write into an existing file (eg one created with File.createTempFile() ), you'll need to pass the REPLACE_EXISTING copy option (otherwise FileAlreadyExistsException is thrown): 要写入现有文件（例如，使用File.createTempFile()创建的文件），您需要传递REPLACE_EXISTING复制选项（否则抛出FileAlreadyExistsException ）：

Files.copy(in, target, StandardCopyOption.REPLACE_EXISTING)

#6楼

Use Commons Net's Util class: 使用Commons Net的Util类：

import org.apache.commons.net.io.Util;...Util.copyStream(in, out);

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