Detecting eof

[jack.smith.sam]

Hi All,

I am using this segment to read a file:

String str
while ((str=in.readLine()!=eof)

but I get error because of eof (I want to detect end of file). How can
I use it?
Also is there any way to detect blank lines in a file? for example:
a

b
If I read the second line is it equal to null or something elase?

Thanks for your help
Jack

 

[Lionel]

Hi All,

I am using this segment to read a file:

String str
while ((str=in.readLine()!=eof)

What is /in/? BufferedReader? I suspect that you want to do:

while((str = in.readLine()) != null)


/in/ is not a very good variable name either.

but I get error because of eof (I want to detect end of file). How can
I use it?
Also is there any way to detect blank lines in a file? for example:
a

b

Well str will equal the empty string "". Or, if the line is full of
spaces you can do str = str.stripWhiteSpace() to be sure that str is the
empty string. Then you do str.equals("") to find out if it is empty or not.

Lionel.

 

[rr news]

Try this.

boolean eof;
eof = false;
try {
while (! eof) {
String str = in.readLine();
if (str == null) {
eof = true;
} else {
System.out.println(str);
}
}
} catch (Exception e) {
System.err.println ("Error: " + e.getMessage());
}


--
---------------------
Jason Herald
www.cingular.com

Hi All,

I am using this segment to read a file:

String str
while ((str=in.readLine()!=eof)

but I get error because of eof (I want to detect end of file). How can
I use it?
Also is there any way to detect blank lines in a file? for example:
a

b
If I read the second line is it equal to null or something elase?

Thanks for your help
Jack

 

[Lionel]

Try this.

boolean eof;
eof = false;
try {
while (! eof) {
String str = in.readLine();
if (str == null) {
eof = true;
} else {
System.out.println(str);
}
}
} catch (Exception e) {
System.err.println ("Error: " + e.getMessage());
}

That while loop seems a whole lot uglier than:

String str;

while((str = in.readLine()) != null) {
System.out.println(str);
}


It's also easier to make a mistake in the body of the while-loop by
doing it that way.

Lionel.

 

[=?ISO-8859-1?Q?Arne_Vajh=F8j?=]

That while loop seems a whole lot uglier than:

String str;

while((str = in.readLine()) != null) {
System.out.println(str);
}


It's also easier to make a mistake in the body of the while-loop by
doing it that way.

I would say that the last code is *the standard* way of
doing it.

Arne

 

[hiwa]

Lionel ã®ãƒ¡ãƒƒã‚»ãƒ¼ã‚¸:

That while loop seems a whole lot uglier than:

String str;

while((str = in.readLine()) != null) {
System.out.println(str);
}


It's also easier to make a mistake in the body of the while-loop by
doing it that way.

Lionel.

Yes, yours is the standard idiom for readLine() usage.
Beware, however, if the original resource has one or more non-canonical
line(s) which do not have a '\n' at the end, readLine() could block
forever or weird Exception could be thrown.

 

[Guest]

Lionel ã®ãƒ¡ãƒƒã‚»ãƒ¼ã‚¸:

Yes, yours is the standard idiom for readLine() usage.
Beware, however, if the original resource has one or more non-canonical
line(s) which do not have a '\n' at the end, readLine() could block
forever or weird Exception could be thrown.

And your solution is different regarding readLine block
or exception how ??

Arne

 

[hiwa]

Arne Vajhøj ã®ãƒ¡ãƒƒã‚»ãƒ¼ã‚¸:

And your solution is different regarding readLine block
or exception how ??

Arne

Oh no. Data canonicalization is often much more important than your
code issue.
I call them 'data bug' issue.

 

[Karl Uppiano]

Hi All,

I am using this segment to read a file:

String str
while ((str=in.readLine()!=eof)

but I get error because of eof (I want to detect end of file). How can
I use it?
Also is there any way to detect blank lines in a file? for example:
a

b
If I read the second line is it equal to null or something elase?

Thanks for your help
Jack

Why not unconditionally spin in a loop and catch the EOFException to break
out?

 

[hiwa]

Karl Uppiano ã®ãƒ¡ãƒƒã‚»ãƒ¼ã‚¸:

Why not unconditionally spin in a loop and catch the EOFException to break
out?

That should only works on some networking situation. It doesn't have
generality.

 

[EJP]

Why not unconditionally spin in a loop and catch the EOFException to break
out?

Because it won't be thrown.

readLine() is defined to return null at EOF, not to throw an EOFException.

 

[Dale King]

Well str will equal the empty string "". Or, if the line is full of spaces
you can do str = str.stripWhiteSpace() to be sure that str is the empty
string. Then you do str.equals("") to find out if it is empty or not.

The method you wanted is called trim, which removes leading and trailing
whitespace from the string.

 

[Lionel]

Because it won't be thrown.

readLine() is defined to return null at EOF, not to throw an EOFException.

You could catch the NullPointerException . . . lol