Number format exception for large inputs

问题

This code works fine for some inputs. but I get a NumberFormatError for higher values of inputs such as 1000000. The input (taken for s[]) ranges from values 1-2000000 What could be the reason?

import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

    public static void main(String[] args) {
        /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution. */

       try
        {
         BufferedReader read = new BufferedReader(new InputStreamReader(System.in));

         int no=Integer.parseInt(read.readLine());

         String s[]=read.readLine().split(" ");

         int result=0;

         for(int i=0; i<no; i++)
         {
             result+= Integer.parseInt(s[i]);
             if(result<0)
                 result=0;
         }
         System.out.println(result);

        }
        catch(IOException e)
       {
           System.out.println(e.getMessage());
       }
    }
}

回答1:

Inside your for-loop, your first entered digit is the size of the array. That's how your logic is so far. Unless you're actually loading in 2,000,000 numbers manually (or copy/pasting), this would throw an ArrayIndexOutOfBoundsException.

You would get a NumberFormatException if you were to type in non-digits as the second input, or a number larger than Integer.MAX_VALUE (2147483647) or less than Integer.MIN_VALUE (-2147483648).

Entering something like:

1000000
2 1 2 1 2 1 /*... 999990 digits later ...*/ 2 1 2 1

makes the program terminate correctly. Here's the input file I used, if anyone wants it: http://ge.tt/95Lr2Kw/v/0

The program was compiles and run manually from a command promt like so: java Solution < in.txt.

Edit: I just remembered that the input values in the array could be as large as 2000000. You would have to use a BigInteger to hold a result value as large as 2000000^2.

回答2:

I am agree with @lzmaki. I don't get any NumberFormatException for your value. But, I get ArrayIndexOutofBoundException which actually caused from StackOverFlow when I tried like this:

1000000
1 2 3
then enter

as in that time, the system recognize that it have not enough memory in its stack for hold such huge number of data.

I got NumberFormatException for the following case:

1000000
enter twice

becuase not system get a non-number format to convert integer format which is "".

I hope my analysis help you to find your bug :)

回答3:

Assuming it's not a buffer overflow, any non-numeric character passed to Integer.parseInt will throw a NumberFormatException. This includes whitespace and non-printable characters like newlines as well as decimal points (Since floating point numbers are not integers).

You can try validating your inputs by using .trim() when you call read.readLine(), as well as checking for null or empty string before passing to Integer.parseInt(). Something like:

     String input = read.readLine();

     if ( input != null )
         input = input.trim();
     if ( input.equals("") )
         throw new IllegalArgumentException("Input must be a number");

     int no=Integer.parseInt( input );

However you decide to validate input for the first line, also do for the second readLine() call. Hopefully you can narrow down exactly what's causing the problem.

来源：https://stackoverflow.com/questions/19607531/number-format-exception-for-large-inputs

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java

netbeans

biginteger

numberformatexception