Whats wrong with this logic - Why the error, out of bounds

Question

Hi there,
I have this code that I am trying to work out with some logic I have put together, as shown below, but I get an error message saying "Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: -29
":" What I am basically trying to do is print out a string which has both numbers and words into a vertical dialog window with the appropriate words next to their corresponding numbers.
{code}
A = "91011Word121314Sentence151617";
int start = 9;
int end = 17;
// Considering that we are on the first iteration
for(int i = start; i <= end; i++)
String a2 = "" + i; // convert the integer 9 into a string
int a1 = A.indexOf(a2); // get the index of 9 in the string A
int a3 = a2.length(); // get the length of 9
int a4 = a1 + a3; // the index of 9 plus its length is "equivalent" to the index of the next number in A -- 1
String a5 = "" + (i+1); // convert the next integer 10 into a string
int a6 = A.indexOf(a5); // get the index of 10 in the string A -- 1
add += a2 + " " + A.substring(a4,a6) + "\n";
/** Following the logic I would expect that at the end of the first iteration the String "add" should contain,
just 9 followed by a space, and the A.substring(1,1) would return nothing since there is no word in the
middle then there will be a new line */
{code}
However, I ended up getting a string index out of bounds exception. I would appreciate it if someone could explain to me why that would be so.
Thanks

Answer 1

define wrote:
for(int i = start; i <= end; i++)
That should probably be "i < end". This program seems very fragile btw. No checking if indexOf() return numbers less than zero, and ambiguous data..
To improve your code, you should use better variable names. Also, it's better to use String.valueOf(i) instead of "" + i
Edited by: paul.miner on Dec 7, 2007 8:53 PM - Typos