The principle and implementation of the LRU cache in the Java class library

LRU (Least Recently Used) cache is a commonly used cache strategy. It determines which data is recently used based on data access time to eliminate when the cache space is insufficient.The Java class library provides a data structure for implementing the LRU cache LinkedhashMap. Here we will introduce the principle of LRU cache and how to achieve it in Java. 1. Principles The principle of LRU cache is based on the order of access time to determine which data should be retained in the cache.When a data is accessed, it will be moved to the end of the cache queue.When the cache space is insufficient, the oldest data will be eliminated, that is, the data located at the head of the queue. 2.java implementation In Java, the LRU cache can be achieved by inheriting the LINKEDHASHMAP class.LinkedhashMap is an orderly hashmap that maintains the order value pair by access order.The following is a simple LRU cache implementation example: import java.util.LinkedHashMap; import java.util.Map; public class LRUCache<K, V> extends LinkedHashMap<K, V> { private final int capacity; public LRUCache(int capacity) { Super (CAPACITY, 0.75F, TRUE); // Specify the access order this.capacity = capacity; } @Override protected boolean removeEldestEntry(Map.Entry<K,V> eldest) { Return size ()> Capacity; // When the capacity exceeds the limit, remove the oldest data } } // test public class Main { public static void main(String[] args) { LRUCache<Integer, String> cache = new LRUCache<>(3); cache.put(1, "A"); cache.put(2, "B"); cache.put(3, "C"); System.out.println (cache); // Output: {1 = a, 2 = b, 3 = c} cache.get (1); // Inquire 1, move it to the end of the queue System.out.println (cache); // Output: {2 = b, 3 = c, 1 = a} cache.put (4, "d"); // Insert new data, cache is full, the oldest data 2 is removed System.out.println (cache); // Output: {3 = c, 1 = a, 4 = d} } } In the above examples, Lrucache inherits LinkedhashMap and maintains orderly in the order of access.By rewriting the Removeldestentry method, we can specify that when the cache size exceeds the capacity, remove the oldest data. Through this implementation, we can easily use the LRU cache strategy in Java to improve data access efficiency.