Scanner class issues

[Pritish Chakraborty]

'Morning everyone

Here's some code straight from K&B -:

import java.util.*;

class ScanNext
{
   public static void main(String[] args)
   {
      boolean b1, b;
      int i;
      String s, hits = "";
      Scanner s1 = new Scanner(args[0]);
      Scanner s2 = new Scanner(args[1]);
      while(b = s1.hasNext());
      {
         s = s1.next();
         hits += "s";
      }
      while(b = s2.hasNext())
      {
         if(s2.hasNextInt())
         {
            i = s2.nextInt();
            hits += "i";
         }
         else if(s2.hasNextBoolean())
         {
            b = s2.nextBoolean();
            hits += "b";
         }
         else
         {
            s2.next();
            hits += "s2";
         }
     }
     System.out.println("Hits = " + hits);
  }
}

It compiles fine, but on trying to execute it-:

E:\Java\jdk1.7.0\bin>java ScanNext "1 true 34 hi"
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 1
at ScanNext.main(ScanNext.java:11)

Why is this exception being thrown? The same code in the book is said to have an output "ssssibis2".

[Anayonkar Shivalkar]

Hello Pritish Chakraborty,

The problem is, because you are providing only one command line argument ("1 true 34 hi" is considered a single argument due to double quotes) and in your code, you are trying to access args[1], and you are getting ArrayIndexOutOfBoundsException.

Are you sure that there are double quotes while running the code, and that there was only one argument?

[Pritish Chakraborty]

Anayonkar, I just realized that I messed up.

In the book, both Scanner objects use args[0] as parameter!

I must've misread it while making notes.

Sorry 'bout that.

[Anayonkar Shivalkar]

Nothing to be sorry about.

On the other hand, after hitting 'submit' button, I realized that I've given you almost a ready-made answer which I shouldn't have done

[gurpeet singh]

is it like double quotes ESCAPES the space character , due to which javac behaves as if it is just a single argument ? is this related to javac or command line feature of windows , just like in bash we use ""(double quotes), ' '(single quotes) or ``(backquotes) for escaping and executing commands. ?

[Pritish Chakraborty]

I don't know/remember whether they act as escapes, but yes, they encapsulate one entire String including whitespaces.