Exception in thread "main" java.lang.NumberFormatException: For input string: ""

Question

Original Question

For the following small code I'm getting the error...

import java.io.*;

class test
{

    public static void main(String args[]) throws IOException 
    {

        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        int i;

        System.out.println("Enter no of processes ");

        int no_of_process=Integer.parseInt(br.readLine());
        int process[]=new int[no_of_process];

        System.out.println("Enter the values");

        for(i=0;i<no_of_process;i++)
            process[i]=Integer.parseInt(br.readLine());

        for(i=0;i<no_of_process;i++)
            System.out.println(process[i]); 

    }
}

Input:

Enter no of processes 
5
Enter the values
1
2
Exception in thread "main" java.lang.NumberFormatException: For input string: ""
at java.lang.NumberFormatException.forInputString(NumberFormatException.java:48)
at java.lang.Integer.parseInt(Integer.java:470)
at java.lang.Integer.parseInt(Integer.java:499)
at test.main(test.java:17)

Process completed.

I think I have written the code properly and proper integer input is also given. How do I get rid of the above error without using any explicit exception handling statements?

Further Question:

Thanks guys for your answers...it is working. But there is one new question in my mind.

I tried the following modification in the code and executed it. To my surprise, input was accepted properly without any run time error.

for(i=0;i<no_of_process;i++)
    {
        System.out.println(Write anything or even keep it blank);
        process[i]=Integer.parseInt(br.readLine());
    }

By adding just one Print statement before (or even after) the input statement in the for loop, my program worked correctly and no exception was thrown while giving input.

Can you guys explain the reason behind this?

Again if I remove the Print statement from there, the same error gets repeated. I am really confused about the reason behind this. Please help.

The program is expecting to read 5 values, but you only give 2, is that correct? — Joni
– Joni, Commented Sep 6, 2013 at 14:31
I gave 2nd and got the exception. No chance to enter the 3rd one — mihir S
– mihir S, Commented Sep 6, 2013 at 20:03

StormeHawke · Accepted Answer · 2015-12-16 15:57:16Z

2

Without any error handling statements? check to see if br.readLine() is returning "" before you attempt to parse it, like so:

String line = br.readLine();
if(!String.isEmpty(line))
{
    //Do stuff
}
else
{
    //Do other stuff
}

edited Dec 16, 2015 at 15:57

answered Sep 6, 2013 at 14:32

StormeHawke

6,2276 gold badges49 silver badges74 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Mauren Over a year ago

He could also use the String.isEmpty() method.

Philipp Sander · Accepted Answer · 2013-09-06 14:45:08Z

0

How to get rid of above error without using any explicit exception handling statements?

for (i = 0; i < no_of_process; i++) {
    String input;
    do {
        input = br.readLine();
        if (isInteger(input)) {
            process[i]=Integer.parseInt(input);
        } else {
            //error handling here
            System.err.println("you entered an invalid input");
        }

    } while(isInteger(input));
}

And isIntegerlooks like this:

public static boolean isInteger(String s)
{
    try {
        Integer.parseInt(s);
    }
    catch (Exception e) {
        return false;
    }

    return true;
}

I think I have written properly and proper integer input is also given.

I think not ;) i think you pressed the return with out typing anything

edited Sep 6, 2013 at 14:45

answered Sep 6, 2013 at 14:33

Philipp Sander

10.3k7 gold badges49 silver badges80 bronze badges

1 Comment

mihir S Over a year ago

ya, i know abt pressing enter without typing anything...i had taken care of that..but still got the same error

MaanooAk · Accepted Answer · 2017-09-11 07:46:35Z

-1

Try this:

import java.io.*;

public class test
{

    public static void main(String args[]) throws IOException 
    {

        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        int i;

        System.out.println("Enter no of processes ");

       try{
        int no_of_process=Integer.parseInt(br.readLine());
        int process[]=new int[no_of_process];

        System.out.println("Enter the values");

        for(i=0;i<no_of_process;i++)
            process[i]=Integer.parseInt(br.readLine());

        for(i=0;i<no_of_process;i++)
            System.out.println(process[i]); 
       }
       catch(NumberFormatException n)
       {
           System.out.println(n.getMessage());
       }

    }
}

edited Sep 11, 2017 at 7:46

MaanooAk

2,46619 silver badges29 bronze badges

answered Sep 11, 2017 at 6:59

ravi jadhav

1

Collectives™ on Stack Overflow

Exception in thread "main" java.lang.NumberFormatException: For input string: ""

Original Question

Further Question:

3 Answers 3

1 Comment

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

Original Question

Further Question:

3 Answers 3

1 Comment

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related