Re: Error with my filter program

From:
Bo Vance <bowman.vance@invalid.invalid>
Newsgroups:
comp.lang.java.help
Date:
Sun, 07 Sep 2008 14:29:50 -0400
Message-ID:
<ga16jt$d0s$1@registered.motzarella.org>
SamuelXiao wrote:

My program is doing filtering.

when I type input.txt, the compiler complains:
Exception in thread "main" java.lang.StringIndexOutOfBoundsException:
String index out of range: -1
        at java.lang.String.substring(String.java:1938)
        at FilterProgram.main(FilterProgram.java:35)
Java Result: 1
How can I fix it and can anyone tell the problem?


SamuelXiao,
   Thank you for posting a compilable example.
Here is a simplified version.

public class Scratch {

   public static void main(String[] args) {
     String tryread =
       "public class Question1{ \t\t/*The parts";
     int doubleslash = tryread.indexOf("//");
     int block1 = tryread.indexOf("/*");
     int block2 = -1;
     if ((doubleslash >= 0) || block1 >= 0) {
       if (doubleslash < block1) {
         tryread = tryread.substring(0, doubleslash);
         System.out.println("doubleslash");
       }
     }
   }
}

at the line: "if (doubleslash < block1) {"
the debugger shows values for:
tryread = "public class Question1{ \t\t/*The parts"
doubleslash = -1
block1 = 30

When I run this program I get:
Exception in thread "main" java.lang.StringIndexOutOfBoundsException:
String index out of range: -1
    at java.lang.String.substring(Unknown Source)
    at Scratch.main(Scratch.java:11)

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