java.io quesion

[afrozkhan khan]

hi!
why the below code gives an error (variable fin not inetialized.) if i comment lines marked //(1) and //(2) .
======================================
import java.io.*;
class filerd
{
public static void main(String s[]) throws IOException
{

FileInputStream fin ;
int i;
try
{
fin = new FileInputStream(s[0]);
}
catch(FileNotFoundException e)
{
System.out.println("file not found");
return;// (1)
}
catch(ArrayIndexOutOfBoundsException e)
{
System.out.println("Usage: filerd filename");
return;// (2)
}

do
{
i = fin.read();
if ( i != -1 ) System.out.print( (char) i );
}
while ( i != -1);
}
}

[Valentin Crettaz]

If an exception gets thrown in the try-block and the return statements on lines 1 and 2 are commented out, it is possible (actually sure) that the variable "fin" might not have been initialized. The compiler is complaining because you are using that variable later in the do-block and you cannot use an uninitialized variable. To remedy to this, you should initialize fin to null when declaring it before the try-block.
If the return statements are not commented out, you can be sure that if no exception happen, fin will be initialize to some value and that if an exception occurs, the method will return and the do-block will never be executed, and thus, the variable "fin" won't be used, so there is no problem with the compiler.