* BAEL-4464 : how to implement LRU-Cache in java codes added * BAEL-4464 : how to implement LRU-Cache in java codes added - package named fixed * BAEL-4464 : how to implement LRU-Cache in java codes added - package named changed * BAEL-4464 : how to implement LRU-Cache in java codes added - unitTest fixed * BAEL-4464 : issues 4,5 fixed. * fixed some issues in BAEL-4464
101 lines
3.1 KiB
Java
101 lines
3.1 KiB
Java
package com.baeldung.lrucache;
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import java.util.Map;
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import java.util.Optional;
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import java.util.concurrent.ConcurrentHashMap;
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import java.util.concurrent.locks.ReentrantReadWriteLock;
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public class LRUCache<K, V> implements Cache<K, V> {
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private int size;
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private Map<K, LinkedListNode<CacheElement<K, V>>> linkedListNodeMap;
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private DoublyLinkedList<CacheElement<K, V>> doublyLinkedList;
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private ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
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public LRUCache(int size) {
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this.size = size;
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this.linkedListNodeMap = new ConcurrentHashMap<>(size);
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this.doublyLinkedList = new DoublyLinkedList<>();
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}
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@Override
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public boolean put(K key, V value) {
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this.lock.writeLock().lock();
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try {
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CacheElement<K, V> item = new CacheElement<K, V>(key, value);
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LinkedListNode<CacheElement<K, V>> newNode;
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if (this.linkedListNodeMap.containsKey(key)) {
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LinkedListNode<CacheElement<K, V>> node = this.linkedListNodeMap.get(key);
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newNode = doublyLinkedList.updateAndMoveToFront(node, item);
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} else {
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if (this.size() >= this.size) {
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this.evictElement();
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}
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newNode = this.doublyLinkedList.add(item);
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}
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if (newNode.isEmpty()) {
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return false;
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}
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this.linkedListNodeMap.put(key, newNode);
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return true;
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} finally {
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this.lock.writeLock().unlock();
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}
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}
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@Override
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public Optional<V> get(K key) {
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this.lock.readLock().lock();
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try {
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LinkedListNode<CacheElement<K, V>> linkedListNode = this.linkedListNodeMap.get(key);
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if (linkedListNode != null && !linkedListNode.isEmpty()) {
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linkedListNodeMap.put(key, this.doublyLinkedList.moveToFront(linkedListNode));
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return Optional.of(linkedListNode.getElement().getValue());
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}
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return Optional.empty();
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} finally {
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this.lock.readLock().unlock();
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}
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}
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@Override
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public int size() {
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this.lock.readLock().lock();
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try {
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return doublyLinkedList.size();
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} finally {
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this.lock.readLock().unlock();
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}
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}
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@Override
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public boolean isEmpty() {
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return size() == 0;
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}
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@Override
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public void clear() {
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this.lock.writeLock().lock();
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try {
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linkedListNodeMap.clear();
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doublyLinkedList.clear();
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} finally {
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this.lock.writeLock().unlock();
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}
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}
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private boolean evictElement() {
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this.lock.writeLock().lock();
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try {
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LinkedListNode<CacheElement<K, V>> linkedListNode = doublyLinkedList.removeTail();
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if (linkedListNode.isEmpty()) {
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return false;
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}
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linkedListNodeMap.remove(linkedListNode.getElement().getKey());
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return true;
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} finally {
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this.lock.writeLock().unlock();
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}
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}
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}
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