[java] UseStringBufferForStringAppends: False Positive with ternary operator

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#1340 [java] UseStringBufferForStringAppends: False Positive with ternary operator

Milestone: PMD-5.3.7

Status: closed

Owner: Andreas Dangel

Labels: java (55)

Module: PMD

Priority: 3-Major

Type: Bug

Affects version:

Ruleset / Rule:

Updated: 2017-01-30

Created: 2015-04-20

Creator: Andreas Dangel

Private: No

Please find the below sample code, which is throwing this exception.

country = (country == null || "".equals(country))
    ? ((String) getCountry())
    : country;

Discussion: https://sourceforge.net/p/pmd/discussion/188193/thread/a1ef16d2/

Related

Discussion: "Prefer StringBuffer over += for concatenating strings" - when using string reassignment with Ternary operator

Discussion

Andreas Dangel - 2015-05-01

status: open --> not-reproducible

assigned_to: Andreas Dangel

Milestone: New Tickets --> PMD-5.3.2
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Andreas Dangel - 2015-05-01

Cannot reproduce with PMD 5.3.1

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Alberto Fernández - 2016-02-26

To trigger the bug, you must define the variable in one statement and perform the append in other.

Here two examples that triggers the bug (tested onsrc/test/resources/net/sourceforge/pmd/lang/java/rule/optimizations/xml/UseStringBufferForStringAppends.xml)

Example1:
public class UseStringBuffer {
public void foo() {
String country = "";
country = (country == null || "".equals(country))
? ((String) getCountry())
: country;
}
}

Example2:
public class UseStringBuffer {
public void foo() {
String country = request.getParameter("country");
country = (country == null) ? "USA" : country;
}
}

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Andreas Dangel - 2016-02-28

status: not-reproducible --> closed

Milestone: PMD-5.3.2 --> PMD-5.3.7

Ruleset / Rule: -->
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Andreas Dangel - 2016-02-28

This bug will be fixed with PMD 5.3.7, 5.4.2 and 5.5.0.

See PR https://github.com/pmd/pmd/pull/85

Last edit: Andreas Dangel 2016-04-30

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Andreas Dangel - 2016-06-25

labels: --> java

summary: UseStringBufferForStringAppends False Positive with ternary operator --> [java] UseStringBufferForStringAppends: False Positive with ternary operator
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David Burström - 2017-01-30

This bug is reproducible with the inverse case on 5.5.3. If you flip the condition and arguments, it will raise a violation.

public class UseStringBuffer {
public void foo() {
String country = request.getParameter("country");
country = (country != null) ? country : "USA";
}
}

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Andreas Dangel - 2017-01-30

Thanks for letting us know. I've create a new ticket over there -> https://github.com/pmd/pmd/issues/222

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