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Hi all, I'm learning Java 2 by myself and find question for help.

I'm testing the System.in.read() method and tried the following program:

import java.io.*;

class ReadBytes {
public static void main(String args[])
throws IOException {
byte data[] = new byte[10];

System.out.println("Enter some characters.");
System.in.read(data);
System.out.print("You entered: ");
for (int i=0; i<data.length; i++) {
System.out.print((char)data[i]);
}
}
}

My question are:
(1) if I just comment out the "throws IOException" in the main, I
just got compilation error! Is the any condition I can tell whether
I have to throw something or not? I remembered in the HelloWOrld
app, I don't have to throw anything.
(2) If I entered more than 10 characters in the above test, I didn't
get overflow error. Why? Actually I'm expected an exception to
be caught.

Thanks in advance.

On Wed, 2 Jun 2004 19:57:12 +0800, M wrote:

> Hi all, I'm learning Java 2 by myself and find question for help.

Please direct your quetions to
c.l.j.help for the moment.
<http://www.physci.org/codes/javafaq.jsp#cljh>

> I'm testing the System.in.read() method and tried the following program:
....
> My question are:
> (1) if I just comment out the "throws IOException" in the main, I
> just got compilation error! Is the any condition I can tell whether
> I have to throw something or not?

'JavaDocs'
<http://java.sun.com/j2se/1.4.2/docs/api/java/lang/System.html#in>
<http://java.sun.com/j2se/1.4.2/docs/api/java/io/InputStream.html#read()>

The second link will most likey break because
of the '()', find your way from here..
<http://java.sun.com/j2se/1.4.2/docs/api/java/io/InputStream.html#method_summary>

> (2) If I entered more than 10 characters in the above test, I didn't
> get overflow error. Why?

Your code only reads the size of the array, 10
characters, then iterates through the existing 10.

Try entering 5..

--
Andrew Thompson
http://www.PhySci.org/ Open-source software suite
http://www.PhySci.org/codes/ Web & IT Help
http://www.1point1C.org/ Science & Technology

M wrote:
> Hi all, I'm learning Java 2 by myself and find question for help.
>
> I'm testing the System.in.read() method and tried the following program:
>
> import java.io.*;
>
> class ReadBytes {
> public static void main(String args[])
> throws IOException {
> byte data[] = new byte[10];
>
> System.out.println("Enter some characters.");
> System.in.read(data);
> System.out.print("You entered: ");
> for (int i=0; i<data.length; i++) {
> System.out.print((char)data[i]);
> }
> }
> }
>
> My question are:
> (1) if I just comment out the "throws IOException" in the main, I
> just got compilation error! Is the any condition I can tell whether
> I have to throw something or not? I remembered in the HelloWOrld
> app, I don't have to throw anything.
> (2) If I entered more than 10 characters in the above test, I didn't
> get overflow error. Why? Actually I'm expected an exception to
> be caught.
>
> Thanks in advance.
>

Read this,
http://java.sun.com/j2se/1.4.2/docs/...html#read(byte[])

it says "public int read(byte[] b) throws IOException", so if you use
it, you have to catch the thrown IOException.

The above article also tells you when & why the method throws the exception.


"Hello world" is here
http://java.sun.com/j2se/1.4.2/docs/...va.lang.String)

It won't throw anything, so you don't need to.


--
Song

More info.:
http://www.dcs.warwick.ac.uk/~esubbn/

Thanks. I'll go thru the spec.

"Yu SONG" <> wrote in message
news:c9kh2o$df4$...
> M wrote:
> > Hi all, I'm learning Java 2 by myself and find question for help.
> >
> > I'm testing the System.in.read() method and tried the following program:
> >
> > import java.io.*;
> >
> > class ReadBytes {
> > public static void main(String args[])
> > throws IOException {
> > byte data[] = new byte[10];
> >
> > System.out.println("Enter some characters.");
> > System.in.read(data);
> > System.out.print("You entered: ");
> > for (int i=0; i<data.length; i++) {
> > System.out.print((char)data[i]);
> > }
> > }
> > }
> >
> > My question are:
> > (1) if I just comment out the "throws IOException" in the main, I
> > just got compilation error! Is the any condition I can tell whether
> > I have to throw something or not? I remembered in the HelloWOrld
> > app, I don't have to throw anything.
> > (2) If I entered more than 10 characters in the above test, I didn't
> > get overflow error. Why? Actually I'm expected an exception to
> > be caught.
> >
> > Thanks in advance.
> >
>
> Read this,
>
http://java.sun.com/j2se/1.4.2/docs/...html#read(byte[]
)
>
> it says "public int read(byte[] b) throws IOException", so if you use
> it, you have to catch the thrown IOException.
>
> The above article also tells you when & why the method throws the
exception.
>
>
> "Hello world" is here
>
http://java.sun.com/j2se/1.4.2/docs/...ml#println(jav
a.lang.String)
>
> It won't throw anything, so you don't need to.
>
>
> --
> Song
>
> More info.:
> http://www.dcs.warwick.ac.uk/~esubbn/
>