Input/output classes
Overview
The family
of stream classes (stream, outStream, inStream)
is used to manage input/output. Three predefined instances of the
"outStream" class correspond to the standard exits (stdOut, stdErr,
stdFile).
The "Stream" class
The "Stream"
class is abstract and provides the following
services.
|
The ... method |
is used to ... |
|
boolean isFile(inString fileName) |
test whether a file exists. Returns true if "fileName" is a normal file which exists, and false in all other cases, including the case where "fileName" is a directory or in the case of E/S errors. |
|
boolean isDirectory(in String directoryName) |
test whether a directory exists. Returns true if "directoryName" is a directory or a network letter ("C:") which exists, and false in all other cases. |
The "outStream" class
The "outStream"
class represents output flows. Its methods
are as follows:
|
The ... method |
is used to ... |
|
boolean open(in String pFileName, in boolean
pAppendMode) |
open the file indicated by "name". If "pAppendMode" is true, this
operation does not reset the file to zero and prepares to write in append
mode. If pAppendMode is false, this operation overwrites the previous
contents and prepares to write in the file.
If the file does not exist, it is created. If the file cannot be opened, false is
returned. The "pFileName" parameter is an
absolute or relative path. The second parameter (pAppendMode) is optional. Its default value is false. |
|
write (in basic_class p1 in basic_class p2, ...) |
write the list of primitive values supplied as parameters. |
|
close () |
close the file. |
|
existFile (in String FileName, out boolean answer) |
test the existence of the file by its name. |
The "inStream" class
The "inStream"
class represents in files. It is used to
read the dataflow stored in the file.
Its methods are as follows:
|
The ...
method |
is
used to ... |
|
boolean open(in String FileName) |
open the file with the indicated name. The file must exist. |
|
read (in String buffer) |
read the file in the "buffer". |
|
close () |
close the file. |
|
existFile (in String FileName,out boolean answer) |
test the existence of a file, using its name. |
Example
We are going
to write different values in a file.
boolean b=true;
int i= 23;
outStream MyFile;
MyFile.open("EXIT");
MyFile.write ("i == ",i, " b == ", b, NL);
MyFile.close();
The result
in the "EXIT" file is as follows:
i == 23 b == true
Note: The "inStream" class combined with "eval" is used to load the formatted data.
Predefined output
The default
output linked to the predefined output corresponds to the output window if J
execution is launched in Objecteering.
|
The ... exit |
corresponds to ... |
|
StdOut |
the predefined output for messages (screen or output window). |
|
StdErr |
the predefined output for error messages. |