试试Cactoos:

new LengthOf(new TeeInput(input, output)).value();

更多详情请访问:http://www.yegor256.com/2017/06/22/object-oriented-input-output-in-cactoos.html

如果你正在使用Java 7，文件(在标准库中)是最好的方法:

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

编辑:当然，当你从文件中创建一个InputStream或OutputStream时，它才有用。使用file. topath()从文件中获取路径。

要写入一个现有的文件(例如用file . createtempfile()创建的文件)，你需要传递REPLACE_EXISTING复制选项(否则会抛出FileAlreadyExistsException):

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

public static boolean copyFile(InputStream inputStream, OutputStream out) {
    byte buf[] = new byte[1024];
    int len;
    long startTime=System.currentTimeMillis();

    try {
        while ((len = inputStream.read(buf)) != -1) {
            out.write(buf, 0, len);
        }

        long endTime=System.currentTimeMillis()-startTime;
        Log.v("","Time taken to transfer all bytes is : "+endTime);
        out.close();
        inputStream.close();

    } catch (IOException e) {

        return false;
    }
    return true;
}

正如Javadoc所指出的那样，PipedInputStream和PipedOutputStream只能在有多个线程时使用。

另外，请注意输入流和输出流不会用ioexception包装任何线程中断…所以，你应该考虑在你的代码中加入中断策略:

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

如果您希望使用这个API复制大量数据，或者从流中复制长时间无法忍受的数据，那么这将是一个有用的补充。

Java 9

自Java 9以来，InputStream提供了一个名为transferTo的方法，具有以下签名:

public long transferTo(OutputStream out) throws IOException

如文档所述，transferTo将:

Reads all bytes from this input stream and writes the bytes to the given output stream in the order that they are read. On return, this input stream will be at end of stream. This method does not close either stream. This method may block indefinitely reading from the input stream, or writing to the output stream. The behavior for the case where the input and/or output stream is asynchronously closed, or the thread interrupted during the transfer, is highly input and output stream specific, and therefore not specified

因此，为了将Java InputStream的内容写入到OutputStream，你可以这样写:

input.transferTo(output);

你可以使用这种方法

public static void copyStream(InputStream is, OutputStream os)
 {
     final int buffer_size=1024;
     try
     {
         byte[] bytes=new byte[buffer_size];
         for(;;)
         {
           int count=is.read(bytes, 0, buffer_size);
           if(count==-1)
               break;
           os.write(bytes, 0, count);
         }
     }
     catch(Exception ex){}
 }