JDK-8214687 : Optimize Collections.nCopies().hashCode() and equals()
- Type: Enhancement
- Component: core-libs
- Sub-Component: java.util:collections
- Affected Version: 8,11,13
- Priority: P4
- Status: Resolved
- Resolution: Fixed
- Submitted: 2018-12-03
- Updated: 2019-10-04
- Resolved: 2018-12-30
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| JDK 11 | JDK 13 | JDK 7 | JDK 8 | Other |
|---|---|---|---|---|
| 11.0.5-oracleFixed | 13 b02Fixed  |
7u241Fixed | 8u231Fixed |
openjdk8u232Fixed |
Description
Currently Collections.nCopies().hashCode() delegates to AbstractList.hashCode() which creates an iterator and caculates the hashCode of the same element n times. An optimized implementation is possible which: - Doesn't create an iterator - Calls element.hashCode() at most once - Has O(log(n)) complexity Also specialized implementation of CopiesList.equals() is possible which at least can check whether another object is also a CopiesList (in this case, no iteration is necessary, just compare single element and size).
Comments
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