Java串行通信API-如果發生超時，inputstream.read（）返回什么？

Question

有人知道串行驅動程序超時時返回的確切值嗎？ 我在Win XP上運行Java1.5。

Answer 1

javadoc說什么？

讀（）

Reads the next byte of data from the input stream. 
The value byte is returned as an int in the range 
0 to 255. If no byte is available because the end 
of the stream has been reached, the value -1 is 
returned. This method blocks until input data 
is available, the end of the stream is detected, 
or an exception is thrown.

A subclass must provide an implementation of this method.

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讀取（字節[]）

Reads some number of bytes from the input stream 
and stores them into the buffer array b. The 
number of bytes actually read is returned as 
an integer. This method blocks until input
data is available, end of file is detected, 
or an exception is thrown. 

If b is null, a NullPointerException is thrown. 
If the length of b is zero, then no bytes 
are read and 0 is returned; otherwise, there is
an attempt to read at least one byte. If no 
byte is available because the stream is at end 
of file, the value -1 is returned; otherwise, 
at least one byte is read and stored into b.

The first byte read is stored into element b[0], 
the next one into b[1], and so on. The number 
of bytes read is, at most, equal to the length 
of b. Let k be the number of bytes actually read;
these bytes will be stored in elements b[0] 
through b[k-1], leaving elements b[k] through 
b[b.length-1] unaffected.

If the first byte cannot be read for any reason 
other than end of file, then an IOException 
is thrown. In particular, an IOException is 
thrown if the input stream has been closed.

The read(b) method for class InputStream 
has the same effect as:

 read(b, 0, b.length)

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讀取（字節[]，整數，整數）

Reads up to len bytes of data from the input 
stream into an array of bytes. An attempt 
is made to read as many as len bytes, but 
a smaller number may be read. The number of bytes 
actually read is returned as an integer.

This method blocks until input data is 
available, end of file is detected, or an exception 
is thrown.

If b is null, a NullPointerException is thrown.

If off is negative, or len is negative, or off+len 
is greater than the length of the array 
b, then an IndexOutOfBoundsException is thrown.

If len is zero, then no bytes are read and 0 is 
returned; otherwise, there is an attempt to 
read at least one byte. If no byte is available 
because the stream is at end of file, the 
value -1 is returned; otherwise, at least one 
byte is read and stored into b.

The first byte read is stored into element b[off], 
the next one into b[off+1], and so on. The number 
of bytes read is, at most, equal to len. Let k be 
the number of bytes actually read; these bytes will
be stored in elements b[off] through b[off+k-1], 
leaving elements b[off+k] through b[off+len-1] unaffected.

In every case, elements b[0] through b[off] and
elements b[off+len] through b[b.length-1] 
are unaffected.

If the first byte cannot be read for any reason other 
than end of file, then an IOException is thrown. In 
particular, an IOException is thrown if the input 
stream has been closed.

The read(b, off, len) method for class InputStream 
simply calls the method read() repeatedly. If the 
first such call results in an IOException, that 
exception is returned from the call to the read(b, off, len) 
method. If any subsequent call to read() results in a 
IOException, the exception is caught and treated as
if it were end of file; the bytes read up to that
point are stored into b and the number of bytes 
read before the exception occurred is returned. 
Subclasses are encouraged to provide a more efficient 
implementation of this method.

本機輸入流沒有超時，因此它取決於驅動程序如何報告結果。 如果驅動程序報告EOF，您將得到-1。 如果驅動程序報告錯誤，則應獲取IOException。

Answer 2

我無法說出確切的值，但我會認為會拋出某種IOException。

如果您是從comm端口獲取輸入流並從中讀取數據，則文檔指出，如果“如果由於文件末尾以外的原因無法讀取第一個字節，則輸入IOException將拋出IOException。已關閉，或者發生了其他一些I / O錯誤。”