java实现简单的LUR算法

public class LRUCache<k,v> extends LinkedHashMap<k,v> {private final int CACHE_SIZE;public LRUCache(int cacheSize){super((int)Math.ceil(cacheSize/0.75)+1,0.75f,true);// 这块就是设置一个hashMap的初始值,同时最后一个true只的是让 LinkedHashMap 按照访问顺序来进行排序,最近访问放在头,最老访问的放在尾巴CACHE_SIZE = cacheSize;}@Overrideprotected boolean removeEldestEntry(Map.Entry eldest) {return  size() >CACHE_SIZE;// 这个意思就是说当map 中的数量大于指定缓存个数的时候,就自动删除最老的数据}
}

 /*** Constructs an empty <tt>LinkedHashMap</tt> instance with the* specified initial capacity, load factor and ordering mode.** @param  initialCapacity the initial capacity* @param  loadFactor      the load factor* @param  accessOrder     the ordering mode - <tt>true</tt> for*         access-order, <tt>false</tt> for insertion-order* @throws IllegalArgumentException if the initial capacity is negative*         or the load factor is nonpositive*/public LinkedHashMap(int initialCapacity,float loadFactor,boolean accessOrder) {super(initialCapacity, loadFactor);this.accessOrder = accessOrder;}

  /*** Returns <tt>true</tt> if this map should remove its eldest entry.* This method is invoked by <tt>put</tt> and <tt>putAll</tt> after* inserting a new entry into the map.  It provides the implementor* with the opportunity to remove the eldest entry each time a new one* is added.  This is useful if the map represents a cache: it allows* the map to reduce memory consumption by deleting stale entries.** <p>Sample use: this override will allow the map to grow up to 100* entries and then delete the eldest entry each time a new entry is* added, maintaining a steady state of 100 entries.* <pre>*     private static final int MAX_ENTRIES = 100;**     protected boolean removeEldestEntry(Map.Entry eldest) {*        return size() &gt; MAX_ENTRIES;*     }* </pre>** <p>This method typically does not modify the map in any way,* instead allowing the map to modify itself as directed by its* return value.  It <i>is</i> permitted for this method to modify* the map directly, but if it does so, it <i>must</i> return* <tt>false</tt> (indicating that the map should not attempt any* further modification).  The effects of returning <tt>true</tt>* after modifying the map from within this method are unspecified.** <p>This implementation merely returns <tt>false</tt> (so that this* map acts like a normal map - the eldest element is never removed).** @param    eldest The least recently inserted entry in the map, or if*           this is an access-ordered map, the least recently accessed*           entry.  This is the entry that will be removed it this*           method returns <tt>true</tt>.  If the map was empty prior*           to the <tt>put</tt> or <tt>putAll</tt> invocation resulting*           in this invocation, this will be the entry that was just*           inserted; in other words, if the map contains a single*           entry, the eldest entry is also the newest.* @return   <tt>true</tt> if the eldest entry should be removed*           from the map; <tt>false</tt> if it should be retained.*/protected boolean removeEldestEntry(Map.Entry<K,V> eldest) {return false;}

示例二：

import java.util.LinkedHashMap;
import java.util.Map;public class LRU extends LinkedHashMap {int capacity;public LRU(int capacity) {super(16, 0.75f, true);this.capacity = capacity;}@Overrideprotected boolean removeEldestEntry(Map.Entry eldest) {return size() > capacity;}public static void main(String[] args) {LRU lru = new LRU(5);lru.put("1", 1);lru.put("2", 2);lru.put("3", 3);lru.put("4", 4);lru.get("1");lru.put("5", 5);lru.put("6", 6);System.out.println(lru.size() + " | " + lru);}
}

感谢: 中华石杉

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