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Add RR cache (#6307)
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KevinMwita7
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package com.thealgorithms.datastructures.caches;
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import java.util.ArrayList;
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import java.util.HashSet;
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import java.util.List;
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import java.util.Random;
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import java.util.Set;
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import org.junit.jupiter.api.Assertions;
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import org.junit.jupiter.api.BeforeEach;
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import org.junit.jupiter.api.Test;
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import org.junit.jupiter.api.function.Executable;
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class RRCacheTest {
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private RRCache<String, String> cache;
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private Set<String> evictedKeys;
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private List<String> evictedValues;
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@BeforeEach
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void setUp() {
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evictedKeys = new HashSet<>();
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evictedValues = new ArrayList<>();
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cache = new RRCache.Builder<String, String>(3)
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.defaultTTL(1000)
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.random(new Random(0))
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.evictionListener((k, v) -> {
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evictedKeys.add(k);
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evictedValues.add(v);
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})
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.build();
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}
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@Test
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void testPutAndGet() {
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cache.put("a", "apple");
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Assertions.assertEquals("apple", cache.get("a"));
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}
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@Test
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void testOverwriteValue() {
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cache.put("a", "apple");
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cache.put("a", "avocado");
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Assertions.assertEquals("avocado", cache.get("a"));
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}
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@Test
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void testExpiration() throws InterruptedException {
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cache.put("temp", "value", 100); // short TTL
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Thread.sleep(200);
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Assertions.assertNull(cache.get("temp"));
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Assertions.assertTrue(evictedKeys.contains("temp"));
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}
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@Test
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void testEvictionOnCapacity() {
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cache.put("a", "alpha");
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cache.put("b", "bravo");
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cache.put("c", "charlie");
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cache.put("d", "delta"); // triggers eviction
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int size = cache.size();
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Assertions.assertEquals(3, size);
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Assertions.assertEquals(1, evictedKeys.size());
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Assertions.assertEquals(1, evictedValues.size());
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}
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@Test
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void testEvictionListener() {
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cache.put("x", "one");
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cache.put("y", "two");
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cache.put("z", "three");
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cache.put("w", "four"); // one of x, y, z will be evicted
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Assertions.assertFalse(evictedKeys.isEmpty());
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Assertions.assertFalse(evictedValues.isEmpty());
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}
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@Test
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void testHitsAndMisses() {
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cache.put("a", "apple");
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Assertions.assertEquals("apple", cache.get("a"));
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Assertions.assertNull(cache.get("b"));
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Assertions.assertEquals(1, cache.getHits());
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Assertions.assertEquals(1, cache.getMisses());
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}
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@Test
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void testSizeExcludesExpired() throws InterruptedException {
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cache.put("a", "a", 100);
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cache.put("b", "b", 100);
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cache.put("c", "c", 100);
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Thread.sleep(150);
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Assertions.assertEquals(0, cache.size());
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}
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@Test
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void testToStringDoesNotExposeExpired() throws InterruptedException {
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cache.put("live", "alive");
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cache.put("dead", "gone", 100);
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Thread.sleep(150);
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String result = cache.toString();
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Assertions.assertTrue(result.contains("live"));
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Assertions.assertFalse(result.contains("dead"));
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}
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@Test
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void testNullKeyGetThrows() {
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Assertions.assertThrows(IllegalArgumentException.class, () -> cache.get(null));
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}
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@Test
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void testPutNullKeyThrows() {
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Assertions.assertThrows(IllegalArgumentException.class, () -> cache.put(null, "v"));
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}
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@Test
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void testPutNullValueThrows() {
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Assertions.assertThrows(IllegalArgumentException.class, () -> cache.put("k", null));
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}
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@Test
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void testPutNegativeTTLThrows() {
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Assertions.assertThrows(IllegalArgumentException.class, () -> cache.put("k", "v", -1));
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}
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@Test
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void testBuilderNegativeCapacityThrows() {
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Assertions.assertThrows(IllegalArgumentException.class, () -> new RRCache.Builder<>(0));
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}
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@Test
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void testBuilderNullRandomThrows() {
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RRCache.Builder<String, String> builder = new RRCache.Builder<>(1);
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Assertions.assertThrows(IllegalArgumentException.class, () -> builder.random(null));
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}
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@Test
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void testBuilderNullEvictionListenerThrows() {
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RRCache.Builder<String, String> builder = new RRCache.Builder<>(1);
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Assertions.assertThrows(IllegalArgumentException.class, () -> builder.evictionListener(null));
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}
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@Test
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void testEvictionListenerExceptionDoesNotCrash() {
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RRCache<String, String> listenerCache = new RRCache.Builder<String, String>(1).evictionListener((k, v) -> { throw new RuntimeException("Exception"); }).build();
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listenerCache.put("a", "a");
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listenerCache.put("b", "b"); // causes eviction but should not crash
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Assertions.assertDoesNotThrow(() -> listenerCache.get("a"));
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}
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@Test
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void testTtlZeroThrowsIllegalArgumentException() {
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Executable exec = () -> new RRCache.Builder<String, String>(3).defaultTTL(-1).build();
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Assertions.assertThrows(IllegalArgumentException.class, exec);
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}
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@Test
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void testPeriodicEvictionStrategyEvictsAtInterval() throws InterruptedException {
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RRCache<String, String> periodicCache = new RRCache.Builder<String, String>(10).defaultTTL(50).evictionStrategy(new RRCache.PeriodicEvictionStrategy<>(3)).build();
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periodicCache.put("x", "1");
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Thread.sleep(100);
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int ev1 = periodicCache.getEvictionStrategy().onAccess(periodicCache);
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int ev2 = periodicCache.getEvictionStrategy().onAccess(periodicCache);
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int ev3 = periodicCache.getEvictionStrategy().onAccess(periodicCache);
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Assertions.assertEquals(0, ev1);
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Assertions.assertEquals(0, ev2);
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Assertions.assertEquals(1, ev3, "Eviction should happen on the 3rd access");
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Assertions.assertEquals(0, periodicCache.size());
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}
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@Test
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void testPeriodicEvictionStrategyThrowsExceptionIfIntervalLessThanOrEqual0() {
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Executable executable = () -> new RRCache.Builder<String, String>(10).defaultTTL(50).evictionStrategy(new RRCache.PeriodicEvictionStrategy<>(0)).build();
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Assertions.assertThrows(IllegalArgumentException.class, executable);
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}
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@Test
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void testNoEvictionStrategyEvictsOnEachCall() throws InterruptedException {
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RRCache<String, String> noEvictionStrategyCache = new RRCache.Builder<String, String>(10).defaultTTL(50).evictionStrategy(new RRCache.NoEvictionStrategy<>()).build();
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noEvictionStrategyCache.put("x", "1");
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Thread.sleep(100);
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int evicted = noEvictionStrategyCache.getEvictionStrategy().onAccess(noEvictionStrategyCache);
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Assertions.assertEquals(1, evicted);
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}
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@Test
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void testBuilderThrowsExceptionIfEvictionStrategyNull() {
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Executable executable = () -> new RRCache.Builder<String, String>(10).defaultTTL(50).evictionStrategy(null).build();
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Assertions.assertThrows(IllegalArgumentException.class, executable);
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}
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@Test
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void testReturnsCorrectStrategyInstance() {
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RRCache.EvictionStrategy<String, String> strategy = new RRCache.NoEvictionStrategy<>();
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RRCache<String, String> newCache = new RRCache.Builder<String, String>(10).defaultTTL(1000).evictionStrategy(strategy).build();
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Assertions.assertSame(strategy, newCache.getEvictionStrategy(), "Returned strategy should be the same instance");
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}
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@Test
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void testDefaultStrategyIsNoEviction() {
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RRCache<String, String> newCache = new RRCache.Builder<String, String>(5).defaultTTL(1000).build();
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Assertions.assertTrue(newCache.getEvictionStrategy() instanceof RRCache.PeriodicEvictionStrategy<String, String>, "Default strategy should be NoEvictionStrategy");
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}
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@Test
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void testGetEvictionStrategyIsNotNull() {
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RRCache<String, String> newCache = new RRCache.Builder<String, String>(5).build();
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Assertions.assertNotNull(newCache.getEvictionStrategy(), "Eviction strategy should never be null");
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}
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}
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