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Thread: Apparent bug?

  1. #1
    Junior Member
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    Default Apparent bug?

    Basically, the program is supposed to ask for the user's name and print it out in reverse and in all lowercase letters.

    However, when I run it, Eclipse makes the debugger open... I get "Source not found."

    Debugger shows this:

    NameReversal [Java Application]
    NameReversal at localhost:52896
    Thread [main] (Suspended (exception StringIndexOutOfBoundsException))
    String.substring(int, int) line: 1762
    NameReversal.main(String[]) line: 13
    /System/Library/Frameworks/JavaVM.framework/Versions/1.5.0/Home/bin/java
    Don't know how there could be an error as line 1762...

    Here's the code:
    import java.io.*;
    import java.util.*;
    public class NameReversal 
    {
    	public static void main(String args[])
    	{
    		Scanner kbreader = new Scanner(System.in);
    		System.out.print("Please enter your name. ");
    		String name = kbreader.nextLine();
    		int howLong = name.length();
    		for(int g=howLong;g>=0;g--)
    		{
    			String reversed = name.substring(g-1,g);
    			System.out.print(reversed.toLowerCase());
    		}
    	}
    }

    Reeaaalllly confused here.


  2. #2
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    Default Re: Apparent bug?

    The error message saying line 1762 is actually referring to the substring method in the String class. Your error is occurring on line 13.

    Your loop goes while g is greater than or equal to 0. Inside the loop you substring from g-1 to g. What happens when g is equal to zero? You try to substring from -1 to 0 which throws a StringIndexOutOfBoundsException.

  3. #3
    Super Moderator Json's Avatar
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    Default Re: Apparent bug?

    Unless you really have to reverse the string like that I would use a StringBuilder instead.

    final StringBuilder stringBuilder = new StringBuilder("String To Reverse");
    final String reversedLowerCasedString = stringBuilder.reverse().toString().toLowerCase();

    // Json