java - FileChannel.close() 是否关闭底层流？

Question

喜欢标题；关闭 FileChannel 是否会关闭底层文件流？

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来自 AbstractInterruptibleChannel.close()您可以阅读的 API 文档:

Closes this channel.

If the channel has already been closed then this method returns immediately. Otherwise it marks the channel as closed and then invokes the implCloseChannel method in order to complete the close operation.

调用 AbstractInterruptibleChannel.implCloseChannel :

Closes this channel.

This method is invoked by the close method in order to perform the actual work of closing the channel. This method is only invoked if the channel has not yet been closed, and it is never invoked more than once.

An implementation of this method must arrange for any other thread that is blocked in an I/O operation upon this channel to return immediately, either by throwing an exception or by returning normally.

这并没有说明有关流的任何内容。所以事实上，当我这样做时:

public static void copyFile(File from, File to) 
        throws IOException, FileNotFoundException {

    FileChannel sc = null;
    FileChannel dc = null;

    try {
        to.createNewFile();

        sc = new FileInputStream(from).getChannel(); 
        dc = new FileOutputStream(to).getChannel();

        long pos = 0;
        long total = sc.size();
        while (pos < total)
            pos += dc.transferFrom(sc, pos, total - pos);

    } finally {
        if (sc != null) 
            sc.close();
        if (dc != null) 
            dc.close();
    }
}

...我让流保持打开状态？

Answer 1

答案是"is"，但 Javadoc 中没有任何内容实际上是这样说的。原因是FileChannel本身是一个抽象类，其具体实现提供了implCloseChannel()方法，关闭了底层FD。然而，由于该架构和 implCloseChannel() 受到保护的事实，这没有得到记录。