Ivan Ponomarev created LANG-1813:
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Summary: `ArrayUtils#hashCode` Javadoc incorrectly states “null
returns zero” (actual result is 629)
Key: LANG-1813
URL: https://issues.apache.org/jira/browse/LANG-1813
Project: Commons Lang
Issue Type: Bug
Components: lang.*
Reporter: Ivan Ponomarev
Since commit 8c6294dd70f986088262a6b75a382cbc9e980543 (dated Jul 19, 2003), the
Javadoc for {{org.apache.commons.lang3.ArrayUtils#hashCode(...)}} states that a
{{null}} array input “returns zero”.
However, this has never been true in practice: the method delegates to {{{}new
HashCodeBuilder().append(array).toHashCode(){}}}, and {{HashCodeBuilder}}
returns *629* for {{null}} input (with its default initial value and
multiplier). This creates a long-standing discrepancy between documented and
actual behavior.
Given the age of the issue and the possibility that some legacy code may rely
on the current behavior, changing the implementation to return 0 for {{null}}
could be a breaking change. The safest resolution appears to be updating the
Javadoc to match actual behavior (i.e., remove the “null returns zero” promise).
Reproducer: the following test fails
{code:java}
@Test
void testNullArrayHashCode() {
// According to javadoc: "null returns zero"
assertEquals(0, ArrayUtils.hashCode(null));
}{code}
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