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https://issues.apache.org/jira/browse/LANG-810?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13411325#comment-13411325
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Krzysztof Nazarewski edited comment on LANG-810 at 7/11/12 9:39 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, 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}
Now tell me what is wrong with the code, because result is:
{code}
Running: StringUtils.join(array, " ", 0, 1);
Result:
array[0]: '0'
array[1]: '1'
Running: StringUtils.join(array, " ", 0, 1);
Result:
array[0]: '0'
array[1]: '1'
Running: StringUtils.join(array, " ", 1, 1);
Result:
array[1]: '1'
array[1]: '1'
Running: StringUtils.join(array, " ", 2, 2);
Result:
array[2]: '2'
array[2]: '2'
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}
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, 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.
{code}
Running: StringUtils.join(array, " ", 0, 1);
Result:
array[0]: '0'
array[1]: '1'
Running: StringUtils.join(array, " ", 0, 1);
Result:
array[0]: '0'
array[1]: '1'
Running: StringUtils.join(array, " ", 1, 1);
Result:
array[1]: '1'
array[1]: '1'
Running: StringUtils.join(array, " ", 2, 2);
Result:
array[2]: '2'
array[2]: '2'
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}
> 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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