<Question>

Why does the NumberFormatException get thrown when the String argument
is not empty?
</Question>

<Background>

I was reading the Sun Tutorial and happened across the section on integers:

http://java.sun.com/docs/books/tutorial/java/nutsandbolts/datatypes.html

I saw the bit on octal and hex representations and thought that I might
be able to take a string containing..oh say "O23" and use the
Integer.parseInt method to convert it to an integer.  After all, the
tutorial does say

 The prefix 0 indicates octal, whereas 0x indicates hexadecimal.

         int decVal = 26;     // The number 26, in decimal
         int octVal = 032;     // The number 26, in octal
         int hexVal = 0x1a;    // The number 26, in hexadecimal

Here's my code:

package just_playing_around;

public class WillThisWork {
    public static void main(String [] args) {
        String s = "O23";
        int x = Integer.parseInt(s.trim());
        System.out.println("s as a string is " + s);
        System.out.println("s as an integer is " + x);
    }
}

And here's the error I get when I run it

Exception in thread "main" java.lang.NumberFormatException: For input
string: "O23"
    at java.lang.NumberFormatException.forInputString(Unknown Source)
    at java.lang.Integer.parseInt(Unknown Source)
    at java.lang.Integer.parseInt(Unknown Source)
    at just_playing_around.WillThisWork.main(WillThisWork.java:6)
</Background>

<Research>
1)  I did a google search on cljp and found the following post

http://groups.google.ca/group/comp.lang.java.programmer/browse_thread/thread/bc2
97073502432fa/d7610d111ecc7ceb?lnk=st&q=java.lang.Integer.parseInt(Unknown+Sourc
e)&rnum=7&hl=en#d7610d111ecc7ceb

If you will notice Patricia's post

    I think this is the critical data. It claims that there was an
    Integer.parseInt call on line 72 with the empty string as input.

    Does that make sense?

    Patricia

2)  I tried to eliminate the probable causes of the "empty string" in
the following sequence

2a)  I removed the parseInt and print for x from my code.

package just_playing_around;

public class WillThisWork {
    public static void main(String [] args) {
        String s = "O23";
//        int x = Integer.parseInt(s.trim());
        System.out.println("s as a string is " + s);
//        System.out.println("s as an integer is " + x);
    }
}

s as a string is O23

2b)  In the same program, I did the trim and assigned the value to a new
string so that I could see what the result of the string was without
disturbing the original.  I also added a comparison to see if indeed
both strings were the same.

package just_playing_around;

public class WillThisWork {
    public static void main(String [] args) {
        String s = "O23";
        String y = s.trim();
        System.out.println("s as a string is " + s);
        System.out.println("y as a string is " + y);
        if (s.equals(y))
        {
            System.out.println("They are the same");
           
        }
        else
        {
            System.out.println("They are different");
        }
    }
}

s as a string is O23
y as a string is O23
They are the same
<Research>
<Theory>
Either the runtime error I am getting is misleading (see Research.1> or
the runtime error is pointing me to something else, something more
insidious.
</Theory>
<Followup>
Where am I going wrong?  Did I mis-read something somewhere or is what I
am trying to do just not do-able using the tools I have available to me
right now?
</Followup>

Thanks for your help