Help regarding indexOf

[gauravj]

Hi, i am New to java and I am parsing a file.The file looks like
=========== file starts ================================
1: Kotloff KL. <-- authors
Bacterial diarrheal pathogens. <-- Title of the paper
Scand J Infect Dis. <-- Journal

2: Ivanoff B.
[Traveller's diarrhea: which vaccines]
J Pak Med Assoc.

3: Fournier JM.
[The current status of research on a cholera vaccine?]
J Pharm Sci.

4: Keddy KH, Koornhof HJ.
Cholera--the new epidemic?.
S Afr Med J.
=========== file ends ================================
The problem i am facing here is that when i am using the "indexOf" for the string to specify ....for the "title of paper"...there are different ending criteria. Is there any why i can specify that the ending criteria is either a " . "(dot) or "]" or a "?". here is my code which works fine if the ending criteria is a "."(dot).but when it comes to " ] " its giving an error which is java.lang.StringIndexOutOfBoundsException: String index out of range: -1
at java.lang.String.substring(String.java:1938)
at TestClass.main(TestClass.java:21)

here is my code.......

// This file uses extractor.java file to format the text file 'result.txt'
// method ext.extract returns the formatted array of strings which I write
// to 'result.txt' file with newline character(\r\n) added.
 
import java.io.*;
 
public class TestClass
{
  public static void main(String [] args)
  {
    extractor ext = new extractor();
    String [] result = ext.extract("myFile.txt");
    try
    {
     int i;
     for(i=0;result[i]!=null;i=i+3)
     {
       int index=0;
       
       String Authors =result[i].substring((result[i].indexOf(':')+3),(result[i].indexOf('.')+1));
       String Title = result[i+1].substring(index,(result[i+1].indexOf('.')));
       String Journal = result[i+2].substring(index,(result[i+2].indexOf('.')+1));
       
       System.out.println(Authors);
       System.out.println(Title);
       System.out.println(Journal);
     }//end of for.
    } //end of try.
    catch(Exception ex)
    {
       ex.printStackTrace();
    }
  }
}

====== the output ========

Kotloff KL. 
Bacterial diarrheal pathogens.
Scand J Infect Dis. 
java.lang.StringIndexOutOfBoundsException: String index out of range: -1
        at java.lang.String.substring(String.java:1938)
        at TestClass.main(TestClass.java:21) 
Press any key to continue...

[JavaBean]

Since the end character can be any of " . "(dot) or "]" or a "?", you need to make sure that you call substring method if the returned value of indexOf is not -1. When indexOf method returns -1, that means the string is not found in the source string and when you try to get substring starting from -1, you get this error, since the minimum valid index is 0 for a string!

So to solve this, first check if indexOf does not return -1 and if so get the substring.