Java nio FileChannel 写入方法说明

Question

I have following code to write by file channel

fc.write(bytebuffer, position);

In several tutorials i referred this is ok and it does the job fine. But in the javadoc https://docs.oracle.com/javase/8/docs/api/java/nio/channels/FileChannel.html#write-java.nio.ByteBuffer-long- this method returns no of bytes written. Therefore my question is, is it possible in some case this will write only part of bytebuffer ? Do i need to wrap this inside a loop ? Is this code has bug waiting to happen ?

Answer 1

The method FileChannel.write(...) implements the method WritableByteChannel.write(...) . This interface can be used for many kinds of channels. The WritableByteChannel.write(...) documentation tells:

Unless otherwise specified, a write operation will return only after writing all of the r requested bytes. Some types of channels, depending upon their state, may write only some of the bytes or possibly none at all. A socket channel in non-blocking mode, for example, cannot write any more bytes than are free in the socket's output buffer.

But in your case with a FileChannel it will always write and returns the remaining element in your ByteBuffer .