StringUtils equals() relies on undefined behavior
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Key: LANG-786
URL: https://issues.apache.org/jira/browse/LANG-786
Project: Commons Lang
Issue Type: Bug
Components: lang.*
Affects Versions: 3.0
Environment: java version "1.7.0_02"
Java(TM) SE Runtime Environment (build 1.7.0_02-b13)
Java HotSpot(TM) 64-Bit Server VM (build 22.0-b10, mixed mode)
Fedora 15 AMD64
Reporter: Daniel Trebbien
Since the {{java.lang.CharSequence}} class was first introduced in 1.4, the
JavaDoc block has contained the following note:
{quote}
This interface does not refine the general contracts of the equals and hashCode
methods. The result of comparing two objects that implement CharSequence is
therefore, in general, undefined. Each object may be implemented by a different
class, and there is no guarantee that each class will be capable of testing its
instances for equality with those of the other.
{quote}
When the signature of the StringUtils equals() method was changed from
{{equals(String, String)}} to {{equals(CharSequence, CharSequence)}} in
R920543, the implementation still relied on calling CharSequence#equals(Object)
even though, in general, the result is undefined.
One example where {{equals(Object)}} returns {{false}} even though, as
CharSequences, two objects represent equal sequences is when one object is an
instance of {{javax.lang.model.element.Name}} and the other object is a String.
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