java - FileOutputStream.getChannel()是否可以返回null？

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7年前关闭。





我正在分析FileOutputStream的API。

getChannel()方法可以返回null吗？如果是这样，在什么情况下？

最佳答案

FileOutputStream getChannel()方法代码

 public FileChannel getChannel() {
    synchronized (this) {
        if (channel == null) {
           channel = FileChannelImpl.open(fd, false, true, this, append);

           /*
             * Increment fd's use count. Invoking the channel's close()
            * method will result in decrementing the use count set for
            * the channel.
             */
            fd.incrementAndGetUseCount();
        }
        return channel;
    }
}

调用FileChannelImpl.open()并且此代码始终创建一个新对象

public static FileChannel open(FileDescriptor fd,
                                boolean readable, boolean writable,
                                Object parent, boolean append)
 {
    return new FileChannelImpl(fd, readable, writable, parent, append);
 }