Q's regarding double/float initialization

I've been programming with Java for quite some time but there's this one among other things that I couldn't find an answer for...

****************************************

import java.io.*;
public class GPA {

public static void main(String a[])throws Exception {
BufferedReader input = new BufferedReader(new InputStreamReader(System.in)) ;
double gpaInput[] = new double[4];
double gpaTot = 0;

for(int ctr = 0; ctr< gpaInput.length; ctr++) {
System.out.println("Input Grade:");
gpaInput[ctr] = Double.parseDouble(input.readLine());
gpaTot += gpaInput[ctr];
}

gpaTot /= gpaInput.length;

System.out.println("Average grade is: " + gpaTot);
}
}

*********************************

The particular code above doesn't seem to have any compiler error, but when I compile I get this:


Unexpected Signal : EXCEPTION_FLT_DIVIDE_BY_ZERO occurred at PC=0x137BEA8
Function=[Unknown.]
Library=(N/A)

NOTE: We are unable to locate the function name symbol for the error
just occurred. Please refer to release documentation for possible
reason and solutions.


Current Java thread:

Dynamic libraries:
0x7CC00000 - 0x7CC1D000 C:\WINDOWS\SYSTEM\IMAGEHLP.DLL

Local Time = Tue May 24 20:31:45 2005
Elapsed Time = 4
#
# HotSpot Virtual Machine Error : EXCEPTION_FLT_DIVIDE_BY_ZERO
# Error ID : 4F530E43505002D5
# Please report this error at
# http://java.sun.com/cgi-bin/bugreport.cgi
#
# Java VM: Java HotSpot(TM) Client VM (1.4.0_02-b02 mixed mode)
#
# An error report file has been saved as hs_err_pid4293351765.log.
# Please refer to the file for further information.
#


To correct the error, I simply change the way gpaTot was initialized:
double gpaTot = 1;

Or, I could make larger alterations by creating an object instead, which is more correct, i know.

****************************************

import java.io.*;
public class GPA {
double gpaInput[] = new double[4];
double gpaTot;

public static void main(String a[])throws Exception {
BufferedReader input = new BufferedReader(new InputStreamReader(System.in)) ;
GPA main = new GPA();

for(int ctr = 0; ctr< main.gpaInput.length; ctr++) {
System.out.println("Input Grade:");
main.gpaInput[ctr] = Double.parseDouble(input.readLine());
main.gpaTot += main.gpaInput[ctr];
}

main.gpaTot /= main.gpaInput.length;

System.out.println("Average grade is: " + main.gpaTot);
}
}

****************************************

It makes me wonder why it happens. I couldn't find the answers on books...they only mentioned that variables have default values but under "some circumstances" they must still be initialized(for local variables). Nobody warned me that i can't initialize double/float to zero (0).

I used jdk1.4.0_02 for the above code. I'll be upgrading it when I have the time.

tnx in advance.

It certainly looks like a bug in the compiler. You should inform Sun about it. There doesn't seem to be any reference to this bug on the Bug Parade

I've compiled and run this successfully on Java 1.5.0_03-b07

Member variables within a class do not have to be initialized. They are initialized by default (doubles to 0.0, boolean to false, integers to 0 etc). Local variables however have to be initialized otherwise you will get a compile time error (variable might not have been initialized).

What happens when you leave it initialized to zero and you do this instead?

gpaTot = gpaTot / gpaInput.length;

I think it's a bug. Even when elongating the equations the unknown exception still occurs. Anyway, our good friend DFavey said it compiled A-OK on jdk1.5 so it doesn't matter anymore. I guess it's been fixed :)

tnx guys.

It also compiles fine in jdk1.4.2_05