Zhongxin Yan created LANG-1804:
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Summary: Fix CharSet#getInstance returns null instead of EMPTY
when input setStrs is null
Key: LANG-1804
URL: https://issues.apache.org/jira/browse/LANG-1804
Project: Commons Lang
Issue Type: Bug
Components: lang.*
Affects Versions: 3.20.0
Reporter: Zhongxin Yan
Attachments: image-2025-12-17-20-03-49-458.png,
image-2025-12-17-20-12-40-410.png, image-2025-12-17-20-13-49-838.png,
image-2025-12-17-20-14-35-234.png
{code:java}
// source code
public static CharSet getInstance(final String... setStrs) {
if (setStrs == null) {
return null; // error
}
if (setStrs.length == 1) {
final CharSet common = COMMON.get(setStrs[0]);
if (common != null) {
return common;
}
}
return new CharSet(setStrs);
} {code}
The {{getInstance}} method of {{CharSet}} currently returns {{null}} when the
input parameter {{setStrs}} is {{{}null{}}}. This behavior contradicts the
documentation, which states that a {{null}} input should return the {{EMPTY}}
constant (an empty character set). Returning {{null}} can lead to
{{NullPointerException}} in calling code that expects a valid {{CharSet}}
instance even for empty inputs.
The Javadoc and source code are as follows：
!image-2025-12-17-20-14-35-234.png|width=441,height=259!
{code:java}
// Test NullPointerException
@Test
void testGetInstance_Null_Fixed_ReturnsEmpty_NoNPE() {
CharSet charSet = CharSet.getInstance(null);
assertThrows(NullPointerException.class,()->charSet.contains('['));
} {code}
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