Mailing-List: contact issues-help@commons.apache.org; run by ezmlm
Precedence: bulk
Reply-To: issues@commons.apache.org
Date: Wed, 11 Jul 2012 09:50:34 +0000 (UTC)
From: "Krzysztof Nazarewski (JIRA)" <jira@apache.org>
To: issues@commons.apache.org
Message-ID: <1703632520.34429.1342000234984.JavaMail.jiratomcat@issues-vm>
In-Reply-To: <1293948079.17813.1341626794829.JavaMail.jiratomcat@issues-vm>
Subject: [jira] [Comment Edited] (LANG-810) StringUtils.join() endIndex,
 bugged for loop
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit


    [ https://issues.apache.org/jira/browse/LANG-810?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13411325#comment-13411325 ] 

Krzysztof Nazarewski edited comment on LANG-810 at 7/11/12 9:49 AM:
--------------------------------------------------------------------

Basically {{endIndex}} takes values from 1 to array.length instead of from 0 to {{(array.length - 1)}}
In current state {{endIndex}} is "1-based index", not "0-based index" while Java language uses 0-based indexes, also previous argument {{startIndex}} is 0-based.

If you put valid endIndex 0, the for loop won't run at all as it checks (i < endIndex) like it was array's length.

Let's say you have 1 element array to join (it does not make practical sense, bu should work), it has index 0 and does not have anything beyond 0 index. 
According to JavaDoc only possible combination of startIndex and endIndex would be (0,0).
{{StringUtils.java, line 3394: for (int i = startIndex; i < endIndex; i++) {}}
However for loop will not execute even single time because {{(i = startIndex = 0)}} is not lower than {{(endIndex = 0)}}, it is equal to endIndex and the result of joining single element array from it's only index 0 to index 0 will be empty string.

Therefore to join that one-element array you need to use combination {{(startIndex = 0, endIndex = 1)}}, where {{(endIndex == array.length)}} is error according to JavaDoc:
"endIndex - the index to stop joining from (exclusive). *It is an error to pass in an end index past the end of the array*"

Example code:
{code:title="test.java"}
import org.apache.commons.lang3.StringUtils;

public class Test {
	public static void main(String[] args) {
		String[] array = new String[] { "0", "1", "2", "3" };

		printResult(array, 0, 0);
		printResult(array, 0, 1);
		printResult(array, 1, 1);
		printResult(array, 2, 3);
		printResult(array, 0, 3);
		printResult(array, 0, 4);
	}

	public static void printResult(String[] array, int startIndex, int endIndex) {
		String str = StringUtils.join(array, " ", startIndex, endIndex);
		System.out.println("Running:\tStringUtils.join(array, \" \", " + startIndex + ", " + endIndex + ");");
		System.out.println("Result: \t" + str);
		System.out.println("array[" + startIndex + "]:\t'" + array[startIndex] + '\'');
		System.out.println("array[" + endIndex + "]:\t'" + array[endIndex] + '\'');
		System.out.println();
	}
}
{code}

Now tell me what is wrong with the code, because result is:
{code}
Running:	StringUtils.join(array, " ", 0, 0);
Result: 	
array[0]:	'0'
array[0]:	'0'

Running:	StringUtils.join(array, " ", 0, 1);
Result: 	0
array[0]:	'0'
array[1]:	'1'

Running:	StringUtils.join(array, " ", 1, 1);
Result: 	
array[1]:	'1'
array[1]:	'1'

Running:	StringUtils.join(array, " ", 2, 3);
Result: 	2
array[2]:	'2'
array[3]:	'3'

Running:	StringUtils.join(array, " ", 0, 3);
Result: 	0 1 2
array[0]:	'0'
array[3]:	'3'

Running:	StringUtils.join(array, " ", 0, 4);
Result: 	0 1 2 3
array[0]:	'0'
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 4
	at Test.printResult(Test.java:20)
	at Test.main(Test.java:12)
{code}

Oh so came up that starting from line 3387:
{code}

        int noOfItems = endIndex - startIndex;
        if (noOfItems <= 0) {
            return EMPTY;
        }
{code}
should be:
{code}

        int noOfItems = endIndex - startIndex + 1;
        if (noOfItems <= 0) {
            return EMPTY;
        }
{code}
because joining one element should return that one exact element, not an empty string.
                
      was (Author: drag0nius):
    Basically {{endIndex}} takes values from 1 to array.length instead of from 0 to {{(array.length - 1)}}
In current state {{endIndex}} is "1-based index", not "0-based index" while Java language uses 0-based indexes, also previous argument {{startIndex}} is 0-based.

If you put valid endIndex 0, the for loop won't run at all as it checks (i < endIndex) like it was array's length.

Let's say you have 1 element array to join (it does not make practical sense, bu should work), it has index 0 and does not have anything beyond 0 index. 
According to JavaDoc only possible combination of startIndex and endIndex would be (0,0).
{{StringUtils.java, line 3394: for (int i = startIndex; i < endIndex; i++) {}}
However for loop will not execute even single time because {{(i = startIndex = 0)}} is not lower than {{(endIndex = 0)}}, it is equal to endIndex and the result of joining single element array from it's only index 0 to index 0 will be empty string.

Therefore to join that one-element array you need to use combination {{(startIndex = 0, endIndex = 1)}}, where {{(endIndex == array.length)}} is error according to JavaDoc:
"endIndex - the index to stop joining from (exclusive). *It is an error to pass in an end index past the end of the array*"

Example code:
{code:title="test.java"}
import org.apache.commons.lang3.StringUtils;

public class Test {
	public static void main(String[] args) {
		String[] array = new String[] { "0", "1", "2", "3" };

		printResult(array, 0, 0);
		printResult(array, 0, 1);
		printResult(array, 1, 1);
		printResult(array, 2, 3);
		printResult(array, 0, 3);
		printResult(array, 0, 4);
	}

	public static void printResult(String[] array, int startIndex, int endIndex) {
		String str = StringUtils.join(array, " ", startIndex, endIndex);
		System.out.println("Running:\tStringUtils.join(array, \" \", " + startIndex + ", " + endIndex + ");");
		System.out.println("Result: \t" + str);
		System.out.println("array[" + startIndex + "]:\t'" + array[startIndex] + '\'');
		System.out.println("array[" + endIndex + "]:\t'" + array[endIndex] + '\'');
		System.out.println();
	}
}
{code}

Now tell me what is wrong with the code, because result is:
{code}
Running:	StringUtils.join(array, " ", 0, 0);
Result: 	
array[0]:	'0'
array[0]:	'0'

Running:	StringUtils.join(array, " ", 0, 1);
Result: 	0
array[0]:	'0'
array[1]:	'1'

Running:	StringUtils.join(array, " ", 1, 1);
Result: 	
array[1]:	'1'
array[1]:	'1'

Running:	StringUtils.join(array, " ", 2, 3);
Result: 	2
array[2]:	'2'
array[3]:	'3'

Running:	StringUtils.join(array, " ", 0, 3);
Result: 	0 1 2
array[0]:	'0'
array[3]:	'3'

Running:	StringUtils.join(array, " ", 0, 4);
Result: 	0 1 2 3
array[0]:	'0'
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 4
	at Test.printResult(Test.java:20)
	at Test.main(Test.java:12)
{code}

Oh so came up that starting from line 3387:
{code}
        int noOfItems = endIndex - startIndex;
        if (noOfItems <= 0) {
            return EMPTY;
        }
{code}
should be:
{code}
        int noOfItems = endIndex - startIndex + 1;
        if (noOfItems <= 0) {
            return EMPTY;
        }
{code}
because joining one element should return that one exact element, not an empty string.
                  
> StringUtils.join() endIndex, bugged for loop
> --------------------------------------------
>
>                 Key: LANG-810
>                 URL: https://issues.apache.org/jira/browse/LANG-810
>             Project: Commons Lang
>          Issue Type: Bug
>          Components: lang.*
>    Affects Versions: 3.1
>            Reporter: Krzysztof Nazarewski
>            Assignee: Joerg Schaible
>   Original Estimate: 1m
>  Remaining Estimate: 1m
>
> endIndex is described as index, but for loop still checks it as "array length".
> Basically missing equal sign
> commons-lang3-3.1-sources.jar, StringUtils.java lines 3309, 3394:
>         for (int i = startIndex; i < endIndex; i++) {
> should be:
>         for (int i = startIndex; i <= endIndex; i++) {

--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators: https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa
For more information on JIRA, see: http://www.atlassian.com/software/jira