这是我最好的机会!!

不要使用inputStream.transferTo(…)，因为它太通用了。 如果你能控制你的缓冲内存，你的代码性能会更好。

public static void transfer(InputStream in, OutputStream out, int buffer) throws IOException {
    byte[] read = new byte[buffer]; // Your buffer size.
    while (0 < (buffer = in.read(read)))
        out.write(read, 0, buffer);
}

当我提前知道流的大小时，我使用这种(可改进的)方法。

public static void transfer(int size, InputStream in, OutputStream out) throws IOException {
    transfer(in, out,
            size > 0xFFFF ? 0xFFFF // 16bits 65,536
                    : size > 0xFFF ? 0xFFF// 12bits 4096
                            : size < 0xFF ? 0xFF // 8bits 256
                                    : size
    );
}

我使用ByteStreamKt。copyTo(src, dst, buffer.length)方法

这是我的代码

public static void replaceCurrentDb(Context context, Uri newDbUri) {
    try {
        File currentDb = context.getDatabasePath(DATABASE_NAME);
        if (currentDb.exists()) {
            InputStream src = context.getContentResolver().openInputStream(newDbUri);
            FileOutputStream dst = new FileOutputStream(currentDb);
            final byte[] buffer = new byte[8 * 1024];
            ByteStreamsKt.copyTo(src, dst, buffer.length);
            src.close();
            dst.close();
            Toast.makeText(context, "SUCCESS! Your selected file is set as current menu.", Toast.LENGTH_LONG).show();
        }
        else
            Log.e("DOWNLOAD:::: Database", " fail, database not found");
    }
    catch (IOException e) {
        Toast.makeText(context, "Data Download FAIL.", Toast.LENGTH_LONG).show();
        Log.e("DOWNLOAD FAIL!!!", "fail, reason:", e);
    }
}

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;
}

我认为这是可行的，但一定要测试一下……轻微的“改进”，但可能会以可读性为代价。

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

使用Java7和try-with-resources，提供了一个简化且可读的版本。

try(InputStream inputStream = new FileInputStream("C:\\mov.mp4");
    OutputStream outputStream = new FileOutputStream("D:\\mov.mp4")) {

    byte[] buffer = new byte[10*1024];

    for (int length; (length = inputStream.read(buffer)) != -1; ) {
        outputStream.write(buffer, 0, length);
    }
} catch (FileNotFoundException exception) {
    exception.printStackTrace();
} catch (IOException ioException) {
    ioException.printStackTrace();
}

JDK使用相同的代码，因此似乎没有“更简单”的方法，没有笨重的第三方库(可能不会做任何不同的事情)。下面是直接从java.nio.file.Files.java中复制的:

// buffer size used for reading and writing
private static final int BUFFER_SIZE = 8192;

/**
  * Reads all bytes from an input stream and writes them to an output stream.
  */
private static long copy(InputStream source, OutputStream sink) throws IOException {
    long nread = 0L;
    byte[] buf = new byte[BUFFER_SIZE];
    int n;
    while ((n = source.read(buf)) > 0) {
        sink.write(buf, 0, n);
        nread += n;
    }
    return nread;
}