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From "Krzysztof Nazarewski (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (LANG-810) StringUtils.join() endIndex, bugged for loop
Date Wed, 11 Jul 2012 09:30:35 GMT

    [ 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 9:29 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 for testing:
{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, 2);
		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}

Run it and tell me what is wrong.
                
      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*"

Let's make some examples:
{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, 2);
		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}

Run it and tell me what is wrong.
                  
> 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++) {

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