├── .github └── workflows │ └── maven.yml ├── .gitignore ├── LICENSE ├── README.md ├── class diagram └── cache-low-level-design.png ├── pom.xml └── src ├── main └── java │ └── com │ └── company │ ├── Main.java │ ├── algorithm │ ├── DoublyLinkedList.java │ ├── DoublyLinkedListNode.java │ └── exception │ │ └── InvalidElementException.java │ └── cache │ ├── Cache.java │ ├── exception │ ├── NotFoundException.java │ └── StorageFullException.java │ ├── factory │ └── CacheFactory.java │ ├── policies │ ├── EvictionPolicy.java │ └── LRUEvictionPolicy.java │ └── storage │ ├── HashMapBasedStorage.java │ └── Storage.java └── test └── java ├── algorithm └── DoublyLinkedListTest.java └── cache ├── CacheTest.java └── policies └── LRUEvictionPolicyTest.java /.github/workflows/maven.yml: -------------------------------------------------------------------------------- 1 | # This workflow will build a Java project with Maven 2 | # For more information see: https://help.github.com/actions/language-and-framework-guides/building-and-testing-java-with-maven 3 | 4 | name: Java CI with Maven 5 | 6 | on: 7 | push: 8 | branches: [ master ] 9 | pull_request: 10 | branches: [ master ] 11 | 12 | jobs: 13 | build: 14 | 15 | runs-on: ubuntu-latest 16 | 17 | steps: 18 | - uses: actions/checkout@v2 19 | - name: Set up JDK 9 20 | uses: actions/setup-java@v1 21 | with: 22 | java-version: 9 23 | - name: Build with Maven 24 | run: mvn test --file pom.xml 25 | -------------------------------------------------------------------------------- /.gitignore: -------------------------------------------------------------------------------- 1 | # Compiled class file 2 | *.class 3 | 4 | # Log file 5 | *.log 6 | 7 | # BlueJ files 8 | *.ctxt 9 | 10 | # Mobile Tools for Java (J2ME) 11 | .mtj.tmp/ 12 | 13 | # Package Files # 14 | *.jar 15 | *.war 16 | *.nar 17 | *.ear 18 | *.zip 19 | *.tar.gz 20 | *.rar 21 | 22 | # virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml 23 | hs_err_pid* 24 | 25 | *# 26 | *.iml 27 | *.ipr 28 | *.iws 29 | *.sw? 30 | *~ 31 | .#* 32 | .*.md.html 33 | .DS_Store 34 | .classpath 35 | .gradle 36 | .idea 37 | .metadata 38 | .project 39 | .recommenders 40 | .settings 41 | /build 42 | /code 43 | MANIFEST.MF 44 | _site/ 45 | activemq-data 46 | bin 47 | build 48 | build.log 49 | dependency-reduced-pom.xml 50 | dump.rdb 51 | interpolated*.xml 52 | lib/ 53 | manifest.yml 54 | overridedb.* 55 | settings.xml 56 | target 57 | transaction-logs 58 | .flattened-pom.xml 59 | secrets.yml 60 | .gradletasknamecache 61 | .sts4-cache 62 | 63 | bin/ 64 | tmp/ 65 | *.tmp 66 | *.bak 67 | *.swp 68 | *~.nib 69 | local.properties 70 | .settings/ 71 | .loadpath 72 | 73 | # External tool builders 74 | .externalToolBuilders/ 75 | 76 | # Locally stored "Eclipse launch configurations" 77 | *.launch 78 | 79 | # PyDev specific (Python IDE for Eclipse) 80 | *.pydevproject 81 | 82 | # CDT-specific (C/C++ Development Tooling) 83 | .cproject 84 | 85 | # CDT- autotools 86 | .autotools 87 | 88 | # Java annotation processor (APT) 89 | .factorypath 90 | 91 | # PDT-specific (PHP Development Tools) 92 | .buildpath 93 | 94 | # sbteclipse plugin 95 | .target 96 | 97 | # Tern plugin 98 | .tern-project 99 | 100 | # TeXlipse plugin 101 | .texlipse 102 | 103 | # STS (Spring Tool Suite) 104 | .springBeans 105 | 106 | # Code Recommenders 107 | .recommenders/ 108 | 109 | # Annotation Processing 110 | .apt_generated/ 111 | 112 | # Scala IDE specific (Scala & Java development for Eclipse) 113 | .cache-main 114 | .scala_dependencies 115 | .worksheet 116 | -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | MIT License 2 | 3 | Copyright (c) 2020 Amar Prakash Pandey 4 | 5 | Permission is hereby granted, free of charge, to any person obtaining a copy 6 | of this software and associated documentation files (the "Software"), to deal 7 | in the Software without restriction, including without limitation the rights 8 | to use, copy, modify, merge, publish, distribute, sublicense, and/or sell 9 | copies of the Software, and to permit persons to whom the Software is 10 | furnished to do so, subject to the following conditions: 11 | 12 | The above copyright notice and this permission notice shall be included in all 13 | copies or substantial portions of the Software. 14 | 15 | THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 16 | IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 17 | FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 18 | AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 19 | LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 20 | OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 21 | SOFTWARE. 22 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # Cache - Low Level System Design 2 | 3 | ###### Class Diagram for low level system design of a cache 4 | 5 | ![cache image](./class%20diagram/cache-low-level-design.png) 6 | 7 | ### Problem Statement 8 | 9 | [Link](https://github.com/anomaly2104/cache-low-level-system-design/blob/master/problem-statement.md) 10 | -------------------------------------------------------------------------------- /class diagram/cache-low-level-design.png: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/amarlearning/cache-low-level-design/9311238448462ee150624f59fe403e6753867033/class diagram/cache-low-level-design.png -------------------------------------------------------------------------------- /pom.xml: -------------------------------------------------------------------------------- 1 | 2 | 5 | 4.0.0 6 | 7 | groupId 8 | cache-low-level-design 9 | 1.0-SNAPSHOT 10 | jar 11 | 12 | 13 | UTF-8 14 | 9 15 | 9 16 | 17 | 18 | 19 | 20 | org.junit.jupiter 21 | junit-jupiter-engine 22 | 5.5.2 23 | test 24 | 25 | 26 | 27 | 28 | 29 | 30 | org.apache.maven.plugins 31 | maven-surefire-plugin 32 | 2.22.0 33 | 34 | 35 | 36 | 37 | 38 | 39 | -------------------------------------------------------------------------------- /src/main/java/com/company/Main.java: -------------------------------------------------------------------------------- 1 | package com.company; 2 | 3 | public class Main { 4 | 5 | public static void main(String[] args) { 6 | // write your code here 7 | } 8 | } 9 | -------------------------------------------------------------------------------- /src/main/java/com/company/algorithm/DoublyLinkedList.java: -------------------------------------------------------------------------------- 1 | package com.company.algorithm; 2 | 3 | import com.company.algorithm.exception.InvalidElementException; 4 | 5 | public class DoublyLinkedList { 6 | 7 | private DoublyLinkedListNode head; 8 | private DoublyLinkedListNode tail; 9 | 10 | public DoublyLinkedList() { 11 | this.head = new DoublyLinkedListNode<>(null); 12 | this.tail = new DoublyLinkedListNode<>(null); 13 | 14 | this.head.next = this.tail; 15 | this.tail.prev = this.head; 16 | } 17 | 18 | /** 19 | * Helper method is detach a node from {@DoubleLinkedList}, 20 | * but the node may still be present in the memory. 21 | * 22 | * @param node 23 | */ 24 | public void detachNode(DoublyLinkedListNode node) { 25 | // simply shifting the pointers 26 | if (node != null) { 27 | node.prev.next = node.next; 28 | node.next.prev = node.prev; 29 | } 30 | } 31 | 32 | /** 33 | * Helper method to add the input node as the last of the {@DoubleLinkedList} 34 | * 35 | * @param node 36 | */ 37 | public void addNodeToLast(DoublyLinkedListNode node) { 38 | node.prev = this.tail.prev; 39 | this.tail.prev.next = node; 40 | 41 | node.next = this.tail; 42 | this.tail.prev = node; 43 | } 44 | 45 | /** 46 | * Helper method to add the element as the last node in this {@DoubleLinkedList}. 47 | * 48 | * @param element 49 | * @return DoubleLinkedList 50 | */ 51 | public DoublyLinkedListNode addElementToLast(E element) { 52 | if (element == null) { 53 | throw new InvalidElementException("Null element cannot be added in list."); 54 | } 55 | 56 | DoublyLinkedListNode node = new DoublyLinkedListNode<>(element); 57 | this.addNodeToLast(node); 58 | 59 | return node; 60 | } 61 | 62 | /** 63 | * Helper method to check if this {@DoubleLinkedList} is empty. 64 | * 65 | * @return 66 | */ 67 | public boolean isEmpty() { 68 | return this.head.next == tail; 69 | } 70 | 71 | /** 72 | * Method to get the first node in the {@DoubleLinkedList} 73 | * 74 | * @return 75 | */ 76 | public DoublyLinkedListNode getFirstNode() { 77 | if (isEmpty()) 78 | return null; 79 | 80 | return this.head.next; 81 | } 82 | 83 | /** 84 | * Method to get the last node in the {@DoubleLinkedList} 85 | * 86 | * @return 87 | */ 88 | public DoublyLinkedListNode getLastNode() { 89 | if (isEmpty()) 90 | return null; 91 | 92 | return this.tail.prev; 93 | } 94 | 95 | } 96 | -------------------------------------------------------------------------------- /src/main/java/com/company/algorithm/DoublyLinkedListNode.java: -------------------------------------------------------------------------------- 1 | package com.company.algorithm; 2 | 3 | /** 4 | * Node structure for the Doubly Linked List. 5 | * 6 | * @param Type Of Key 7 | */ 8 | public class DoublyLinkedListNode { 9 | 10 | private final E element; 11 | DoublyLinkedListNode next; 12 | DoublyLinkedListNode prev; 13 | 14 | public DoublyLinkedListNode(E element) { 15 | this.element = element; 16 | this.next = null; 17 | this.prev = null; 18 | } 19 | 20 | public E getElement() { 21 | return element; 22 | } 23 | 24 | public DoublyLinkedListNode getNext() { 25 | return next; 26 | } 27 | 28 | public DoublyLinkedListNode getPrev() { 29 | return prev; 30 | } 31 | } 32 | 33 | 34 | -------------------------------------------------------------------------------- /src/main/java/com/company/algorithm/exception/InvalidElementException.java: -------------------------------------------------------------------------------- 1 | package com.company.algorithm.exception; 2 | 3 | public class InvalidElementException extends RuntimeException { 4 | 5 | public InvalidElementException(final String message) { 6 | super(message); 7 | } 8 | 9 | } 10 | -------------------------------------------------------------------------------- /src/main/java/com/company/cache/Cache.java: -------------------------------------------------------------------------------- 1 | package com.company.cache; 2 | 3 | import com.company.cache.exception.NotFoundException; 4 | import com.company.cache.exception.StorageFullException; 5 | import com.company.cache.policies.EvictionPolicy; 6 | import com.company.cache.storage.Storage; 7 | 8 | public class Cache { 9 | 10 | private final Storage storage; 11 | private final EvictionPolicy evictionPolicy; 12 | 13 | public Cache(Storage storage, EvictionPolicy evictionPolicy) { 14 | this.storage = storage; 15 | this.evictionPolicy = evictionPolicy; 16 | } 17 | 18 | public void put(K key, V value) { 19 | try { 20 | this.storage.put(key, value); 21 | this.evictionPolicy.keyAccessed(key); 22 | } catch (StorageFullException e) { 23 | K keyToRemove = this.evictionPolicy.removeKey(); 24 | if (keyToRemove == null) { 25 | throw new RuntimeException("Unexpected state. Storage full and key is not evicting."); 26 | } 27 | this.storage.remove(keyToRemove); 28 | put(key, value); 29 | } 30 | } 31 | 32 | public V get(K key) { 33 | V value = null; 34 | try { 35 | value = this.storage.get(key); 36 | this.evictionPolicy.keyAccessed(key); 37 | } catch (NotFoundException e) { 38 | System.out.println("Key you are looking for, is not present in storage."); 39 | } 40 | 41 | return value; 42 | } 43 | 44 | } 45 | -------------------------------------------------------------------------------- /src/main/java/com/company/cache/exception/NotFoundException.java: -------------------------------------------------------------------------------- 1 | package com.company.cache.exception; 2 | 3 | public class NotFoundException extends RuntimeException { 4 | 5 | public NotFoundException(final String message) { 6 | super(message); 7 | } 8 | 9 | } 10 | -------------------------------------------------------------------------------- /src/main/java/com/company/cache/exception/StorageFullException.java: -------------------------------------------------------------------------------- 1 | package com.company.cache.exception; 2 | 3 | public class StorageFullException extends RuntimeException { 4 | 5 | public StorageFullException(final String message) { 6 | super(message); 7 | } 8 | 9 | } 10 | -------------------------------------------------------------------------------- /src/main/java/com/company/cache/factory/CacheFactory.java: -------------------------------------------------------------------------------- 1 | package com.company.cache.factory; 2 | 3 | import com.company.cache.Cache; 4 | import com.company.cache.policies.LRUEvictionPolicy; 5 | import com.company.cache.storage.HashMapBasedStorage; 6 | 7 | public class CacheFactory { 8 | public Cache defaultCache(final int capacity) { 9 | return new Cache(new HashMapBasedStorage(capacity), new LRUEvictionPolicy()); 10 | } 11 | } 12 | -------------------------------------------------------------------------------- /src/main/java/com/company/cache/policies/EvictionPolicy.java: -------------------------------------------------------------------------------- 1 | package com.company.cache.policies; 2 | 3 | 4 | /** 5 | * Interface to define eviction policy. 6 | * 7 | * @param Type of Key. 8 | */ 9 | public interface EvictionPolicy { 10 | 11 | /** 12 | * Add the key in the eviction policy. 13 | * 14 | * @param key 15 | */ 16 | void keyAccessed(K key); 17 | 18 | 19 | /** 20 | * Remove the key from the eviction policy and return it. 21 | * 22 | * @return Type of Key. 23 | */ 24 | K removeKey(); 25 | 26 | } 27 | -------------------------------------------------------------------------------- /src/main/java/com/company/cache/policies/LRUEvictionPolicy.java: -------------------------------------------------------------------------------- 1 | package com.company.cache.policies; 2 | 3 | import com.company.algorithm.DoublyLinkedList; 4 | import com.company.algorithm.DoublyLinkedListNode; 5 | 6 | import java.util.HashMap; 7 | import java.util.Map; 8 | 9 | public class LRUEvictionPolicy implements EvictionPolicy { 10 | 11 | private final DoublyLinkedList dll; 12 | private final Map> nodeMap; 13 | 14 | public LRUEvictionPolicy() { 15 | this.nodeMap = new HashMap<>(); 16 | this.dll = new DoublyLinkedList<>(); 17 | } 18 | 19 | @Override 20 | public void keyAccessed(K key) { 21 | DoublyLinkedListNode node; 22 | 23 | if (nodeMap.containsKey(key)) { 24 | node = nodeMap.get(key); 25 | dll.detachNode(node); 26 | dll.addNodeToLast(node); 27 | } else { 28 | node = dll.addElementToLast(key); 29 | nodeMap.put(key, node); 30 | } 31 | } 32 | 33 | @Override 34 | public K removeKey() { 35 | DoublyLinkedListNode firstNode = dll.getFirstNode(); 36 | if (firstNode == null) { 37 | return null; 38 | } 39 | dll.detachNode(firstNode); 40 | return firstNode.getElement(); 41 | } 42 | } 43 | -------------------------------------------------------------------------------- /src/main/java/com/company/cache/storage/HashMapBasedStorage.java: -------------------------------------------------------------------------------- 1 | package com.company.cache.storage; 2 | 3 | import com.company.cache.exception.NotFoundException; 4 | import com.company.cache.exception.StorageFullException; 5 | 6 | import java.util.HashMap; 7 | import java.util.Map; 8 | 9 | public class HashMapBasedStorage implements Storage { 10 | 11 | private final Integer capacity; 12 | private final Map storage; 13 | 14 | public HashMapBasedStorage(Integer capacity) { 15 | this.capacity = capacity; 16 | this.storage = new HashMap<>(); 17 | } 18 | 19 | @Override 20 | public void put(K key, V value) { 21 | if (isStorageFull()) throw new StorageFullException("Storage capacity is full."); 22 | this.storage.put(key, value); 23 | } 24 | 25 | @Override 26 | public void remove(K key) { 27 | if (!this.storage.containsKey(key)) throw new NotFoundException("No value cached with that key."); 28 | this.storage.remove(key); 29 | } 30 | 31 | @Override 32 | public V get(K key) { 33 | if (!this.storage.containsKey(key)) throw new NotFoundException("No value cached with that key."); 34 | return this.storage.get(key); 35 | } 36 | 37 | private boolean isStorageFull() { 38 | return this.storage.size() == capacity; 39 | } 40 | } 41 | -------------------------------------------------------------------------------- /src/main/java/com/company/cache/storage/Storage.java: -------------------------------------------------------------------------------- 1 | package com.company.cache.storage; 2 | 3 | import com.company.cache.exception.NotFoundException; 4 | import com.company.cache.exception.StorageFullException; 5 | 6 | /** 7 | * Interface used to manage storage of our application. 8 | * 9 | * @param Type of Key. 10 | * @param Type of Value. 11 | */ 12 | public interface Storage { 13 | 14 | /** 15 | * Method used to add new cache in storage. 16 | * 17 | * @param key 18 | * @param value 19 | * @throws StorageFullException 20 | */ 21 | void put(K key, V value); 22 | 23 | /** 24 | * Method used to remove an entry from the storage. 25 | * 26 | * @param key 27 | * @throws NotFoundException 28 | */ 29 | void remove(K key); 30 | 31 | /** 32 | * Method used to get Value based on Key from storage. 33 | * 34 | * @param key 35 | * @return 36 | * @throws NotFoundException 37 | */ 38 | V get(K key); 39 | 40 | } 41 | -------------------------------------------------------------------------------- /src/test/java/algorithm/DoublyLinkedListTest.java: -------------------------------------------------------------------------------- 1 | package algorithm; 2 | 3 | import com.company.algorithm.DoublyLinkedList; 4 | import com.company.algorithm.DoublyLinkedListNode; 5 | import org.junit.jupiter.api.BeforeEach; 6 | import org.junit.jupiter.api.Test; 7 | 8 | import java.util.Collections; 9 | import java.util.List; 10 | import java.util.Optional; 11 | 12 | import static org.junit.jupiter.api.Assertions.assertEquals; 13 | 14 | 15 | class DoublyLinkedListTest { 16 | 17 | DoublyLinkedList dll; 18 | 19 | @BeforeEach 20 | void setup() { 21 | dll = new DoublyLinkedList<>(); 22 | } 23 | 24 | @Test 25 | void test_doublyLinkedListAddNode() { 26 | 27 | // Given 28 | DoublyLinkedListNode node1 = new DoublyLinkedListNode<>(1); 29 | DoublyLinkedListNode node2 = new DoublyLinkedListNode<>(2); 30 | DoublyLinkedListNode node3 = new DoublyLinkedListNode<>(3); 31 | DoublyLinkedListNode node4 = new DoublyLinkedListNode<>(4); 32 | 33 | // When, then 34 | dll.addNodeToLast(node1); 35 | verifyDll(dll, Collections.unmodifiableList(List.of(1))); 36 | 37 | // When, then 38 | dll.addNodeToLast(node2); 39 | verifyDll(dll, Collections.unmodifiableList(List.of(1, 2))); 40 | 41 | // When, then 42 | dll.addNodeToLast(node3); 43 | verifyDll(dll, Collections.unmodifiableList(List.of(1, 2, 3))); 44 | 45 | // When, then 46 | dll.addNodeToLast(node4); 47 | verifyDll(dll, Collections.unmodifiableList(List.of(1, 2, 3, 4))); 48 | } 49 | 50 | @Test 51 | void test_doublyLinkedListDetachNode() { 52 | 53 | // Given 54 | DoublyLinkedListNode node1 = new DoublyLinkedListNode<>(1); 55 | DoublyLinkedListNode node2 = new DoublyLinkedListNode<>(2); 56 | DoublyLinkedListNode node3 = new DoublyLinkedListNode<>(3); 57 | DoublyLinkedListNode node4 = new DoublyLinkedListNode<>(4); 58 | 59 | dll.addNodeToLast(node1); 60 | dll.addNodeToLast(node2); 61 | dll.addNodeToLast(node3); 62 | dll.addNodeToLast(node4); 63 | 64 | // then 65 | verifyDll(dll, Collections.unmodifiableList(List.of(1, 2, 3, 4))); 66 | 67 | // when, then 68 | dll.detachNode(node1); 69 | verifyDll(dll, Collections.unmodifiableList(List.of(2, 3, 4))); 70 | 71 | // when, then 72 | dll.detachNode(node3); 73 | verifyDll(dll, Collections.unmodifiableList(List.of(2, 4))); 74 | 75 | // when, then 76 | dll.detachNode(null); 77 | verifyDll(dll, Collections.unmodifiableList(List.of(2, 4))); 78 | 79 | } 80 | 81 | private void verifyDll(DoublyLinkedList dll, List unmodifiableList) { 82 | assertEquals(dll.getFirstNode().getElement(), unmodifiableList.get(0)); 83 | assertEquals(dll.getLastNode().getElement(), unmodifiableList.get(unmodifiableList.size() - 1)); 84 | 85 | DoublyLinkedListNode currentNode = dll.getFirstNode(); 86 | 87 | for (Integer element : unmodifiableList) { 88 | assertEquals(element, currentNode.getElement()); 89 | currentNode = currentNode.getNext(); 90 | } 91 | } 92 | } 93 | -------------------------------------------------------------------------------- /src/test/java/cache/CacheTest.java: -------------------------------------------------------------------------------- 1 | package cache; 2 | 3 | import com.company.cache.Cache; 4 | import com.company.cache.factory.CacheFactory; 5 | import org.junit.jupiter.api.BeforeEach; 6 | import org.junit.jupiter.api.Test; 7 | 8 | import static org.junit.jupiter.api.Assertions.assertEquals; 9 | import static org.junit.jupiter.api.Assertions.assertNull; 10 | 11 | public class CacheTest { 12 | 13 | Cache cache; 14 | 15 | @BeforeEach 16 | public void setup() { 17 | cache = new CacheFactory().defaultCache(5); 18 | } 19 | 20 | @Test 21 | void test_itShouldBeAbleToGetItemsFromCache() { 22 | // When 23 | cache.put(1, 1); 24 | cache.put(2, 2); 25 | cache.put(3, 3); 26 | 27 | // Then 28 | assertEquals(1, cache.get(1)); 29 | assertEquals(2, cache.get(2)); 30 | assertEquals(3, cache.get(3)); 31 | 32 | // When 33 | cache.put(4, 4); 34 | cache.put(5, 5); 35 | 36 | // Then 37 | assertEquals(4, cache.get(4)); 38 | assertEquals(5, cache.get(5)); 39 | 40 | // Since, we have used our cache to full capacity, 41 | // It will remove the last accessed element to insert new. 42 | 43 | // When 44 | cache.put(6, 6); 45 | 46 | // Then, Key 1 should be removed by now. 47 | assertNull(cache.get(1)); 48 | } 49 | 50 | } 51 | -------------------------------------------------------------------------------- /src/test/java/cache/policies/LRUEvictionPolicyTest.java: -------------------------------------------------------------------------------- 1 | package cache.policies; 2 | 3 | import com.company.cache.policies.LRUEvictionPolicy; 4 | import org.junit.jupiter.api.BeforeEach; 5 | import org.junit.jupiter.api.Test; 6 | 7 | import static org.junit.jupiter.api.Assertions.assertEquals; 8 | import static org.junit.jupiter.api.Assertions.assertNull; 9 | 10 | class LRUEvictionPolicyTest { 11 | 12 | LRUEvictionPolicy evictionPolicy; 13 | 14 | @BeforeEach 15 | public void setup() { 16 | evictionPolicy = new LRUEvictionPolicy<>(); 17 | } 18 | 19 | @Test 20 | void test_noKeysEvictionInitially() { 21 | // Then 22 | assertNull(evictionPolicy.removeKey()); 23 | } 24 | 25 | @Test 26 | void test_keyEvictionInSameOrderTheyAreAccessed() { 27 | 28 | // When 29 | evictionPolicy.keyAccessed(1); 30 | evictionPolicy.keyAccessed(2); 31 | evictionPolicy.keyAccessed(3); 32 | evictionPolicy.keyAccessed(4); 33 | evictionPolicy.keyAccessed(5); 34 | 35 | // Then 36 | assertEquals(1, evictionPolicy.removeKey()); 37 | assertEquals(2, evictionPolicy.removeKey()); 38 | assertEquals(3, evictionPolicy.removeKey()); 39 | assertEquals(4, evictionPolicy.removeKey()); 40 | assertEquals(5, evictionPolicy.removeKey()); 41 | } 42 | 43 | @Test 44 | void test_keyEvictionOrderIfReAccessed() { 45 | 46 | // When 47 | evictionPolicy.keyAccessed(1); 48 | evictionPolicy.keyAccessed(2); 49 | evictionPolicy.keyAccessed(3); 50 | evictionPolicy.keyAccessed(2); 51 | evictionPolicy.keyAccessed(1); 52 | evictionPolicy.keyAccessed(4); 53 | evictionPolicy.keyAccessed(5); 54 | evictionPolicy.keyAccessed(1); 55 | 56 | // Then 57 | assertEquals(3, evictionPolicy.removeKey()); 58 | assertEquals(2, evictionPolicy.removeKey()); 59 | assertEquals(4, evictionPolicy.removeKey()); 60 | assertEquals(5, evictionPolicy.removeKey()); 61 | assertEquals(1, evictionPolicy.removeKey()); 62 | } 63 | 64 | } 65 | --------------------------------------------------------------------------------