odd n even numbers program

[prerna boja]

Hi all,

I wrote the following program. I need to get the number of odd n even numbers from "data.in" file .

I am getting an exception as :Exception in thread "main" java.lang.StringIndexoutofBoundsException : index out of range:-1
at java.lang.String.substring<String.java:1768>
at oddeven.main<oddeven.java:23>

import java.io.*;
public class OddEven
{
  public static BufferedReader inFile;
  public static PrintWriter outFile;
  public static void main(String[] args) throws IOException
  {
boolean goOn = true;
int oddCount=0;
int evenCount=0;
int oddsum=0;
int evensum=0;
int loc;
String work;
int value;
inFile = new BufferedReader(new FileReader("data.in"));
    outFile = new PrintWriter(new FileWriter("data.out"));
    String inputString = inFile.readLine();
 
    while (goOn)
    {
      loc = inputString.indexOf(',');
  work = inputString.substring(0,loc);// catch the string
  value = Integer.parseInt(work ); // convert to integer
     if(value % 2 == 1)
     {
 oddCount++;
 oddsum= oddsum+value;
 
  }
 else
 {
evenCount++;
evensum = evensum + value;
     }
 
} // while()
 
outFile.println("for even  numbers" +evenCount);
outFile.println("for even  numbers" +evensum);
outFile.println("for odd numbers" +oddCount );
outFile.println("for even  numbers" +oddsum);
inFile.close();
outFile.close();
    }
}
 
  

data.in file contains :The first data value is
1066
The second data value is
1492
The third data value is
1939
The fourth data value is
1944
The fifth data value is
2000

help me out

[Stan James]

This is pretty good information:

java.lang.StringIndexoutofBoundsException : index out of range:-1
at java.lang.String.substring<String.java:1768>
at oddeven.main<oddeven.java:23>

Ignore the String info since you didn't write that. What's happening at your line 23 with an index that might be -1?

work = inputString.substring(0,loc);// catch the string 

Look up a line to see how it maybe got to be -1. I think your code does not match your input file layout. See if that helps!

[prerna boja]

Hi ,

I tried to chage the program. It is compiling n giving no exception, but I amnot getting the output.

 public static PrintWriter outFile;
  public static void main(String[] args) throws IOException
  {
int count = 0;
int sum = 0;
boolean notDone = true;
int value;
inFile = new BufferedReader(new FileReader("data.in"));
outFile = new PrintWriter(new FileWriter("data.out"));
    while(notDone)
    {
String inputString = inFile.readLine();
if(inputString == null)
{
int loc;
String work;
        loc = inputString.indexOf("The First data value is ");
work = inputString.substring(0,loc);
    value = Integer.parseInt(work);
if(inputString != null)
 {
  value = Integer.parseInt(work);
if(value % 2 == 0)
{
         count++;
 sum = sum + value;
 notDone = (count < 5);
 outFile.println("The odd  numbers are" + sum);
 outFile.println(count);
}
}
}
else
{
outFile.println("for odd  numbers" +sum);
notDone = false;
}
}
inFile.close();
outFile.close();
    }
}
 
  

[Henry Wong]

Originally posted by prerna boja:
Hi ,

I tried to chage the program. It is compiling n giving no exception, but I amnot getting the output.

Prerna, I don't think you fixed the problem. In fact, I think it is worse. I believe the reason why you are not getting anymore exceptions is because the code in question is no longer running.

BTW, you should fix the idents. It is very difficult to read.

Henry

[Henry Wong]

Opps, Sorry. Forgot to give a hint to help you fix the problem.

String inputString = inFile.readLine();
if(inputString == null) 
{
    ...

When does readLine() return null? And is the logic that you want to handle the null, in the "if", or the "else"?

Henry

[Adam Vinueza]

Your first problem is that the code you've given reads only the first number forever: you never change inputString. Strictly speaking, you can't change it--Strings are immutable--but you could at least replace it with another String that's shorter. If you're just starting out, try the substring() method; if you're feeling fancy, you could do it the correct way, which is by using a StringBuffer.

I have no idea how you got a runtime error with the code you've given; I ran it on my JVM and it just kept reading the first number for ever and ever. But in this context, -1 should indicate either that you've reached end-of-file or that inputString.indexOf(loc) can't find the loc substring.

Whenever you see a -1, you should check the API to see what values your function calls might be returning. In general, beginning Java programmers should always code with the API right in front of them at all times.