StringIndexOutOfBoundsException

StringIndexOutOfBoundsException: String Index out of range: 13

I'm getting this error on the following code:

public URLReader(String URL){

String inputLine;

int k, inicioNome, tamURL = URL.length();

System.out.println(tamURL);// <- Displays the right value

System.out.println(URL);// <- Displays the right value

System.out.println(URL.charAt(1));// <- Displays the right value

System.out.println(URL.substring(1,12)); // <- Displays the right value

for(k=tamURL+1;k>0;k--)

if((URL.charAt(k) == '/') || (URL.charAt(k) == '\\'))//### <- Here is the problem....

inicioNome = k;

...

Do You know what is wrong...

[745 byte] By [Naberus666] at [2007-9-30 4:15:58]