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Add cache with LIFO replacement policy #6390

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Description

This PR adds a reusable LIFOCache implementation with the following features:

  • Fixed size LIFO eviction policy using Deque as stack and HashMap as cache

  • Time to live (TTL)

  • Thread-safe operations using ReentrantLock

  • Pluggable EvictionStrategy to control expired entry cleanup

  • Eviction listener callback support for observing removals

  • Hit and miss statistics tracking

  • Builder for flexible configuration

  • I have read CONTRIBUTING.md.

  • This pull request is all my own work -- I have not plagiarized it.

  • All filenames are in PascalCase.

  • All functions and variable names follow Java naming conventions.

  • All new algorithms have a URL in their comments that points to Wikipedia or other similar explanations.

  • All new code is formatted with clang-format -i --style=file path/to/your/file.java

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codecov-commenter commented Jul 15, 2025

Codecov Report

Attention: Patch coverage is 98.05195% with 3 lines in your changes missing coverage. Please review.

Project coverage is 75.05%. Comparing base (31bf130) to head (8c3f312).

Files with missing lines Patch % Lines
...thealgorithms/datastructures/caches/LIFOCache.java 98.05% 0 Missing and 3 partials ⚠️
Additional details and impacted files
@@             Coverage Diff              @@
##             master    #6390      +/-   ##
============================================
+ Coverage     74.86%   75.05%   +0.19%     
- Complexity     5482     5517      +35     
============================================
  Files           682      683       +1     
  Lines         19012    19166     +154     
  Branches       3670     3693      +23     
============================================
+ Hits          14233    14385     +152     
  Misses         4224     4224              
- Partials        555      557       +2     

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@KevinMwita7 KevinMwita7 marked this pull request as ready for review July 15, 2025 13:08

while (it.hasNext()) {
K k = it.next();
CacheEntry<V> entry = cache.get(k);
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@DenizAltunkapan DenizAltunkapan Jul 20, 2025

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Try using the final keyword for local variables where possible @KevinMwita7

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private LIFOCache(Builder<K, V> builder) {
this.capacity = builder.capacity;
this.defaultTTL = builder.defaultTTL;
this.cache = HashMap.newHashMap(builder.capacity);
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I didn't know there is such static method... A suggestion could be using the classic constructor new HashMap<>(builder.capacity)

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I think it was introduced in Java 19. But I've changed it to in which java version was HashMap.newHashMap introduced

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3 participants