Android LRUCache Class Analysis

 Public classLurcache<k, v> {    PrivateFinal Linkedhashmap<k, v>map; Private intSize//size that has been stored    Private intMaxSize;//Maximum storage space specified    Private intPutcount;//number of Put    Private intCreatecount;//Number of Create    Private intEvictioncount;//Number of recoveries    Private intHitCount;//Number of hits    Private intMisscount;//Number of Lost     PublicLruCache (intmaxSize) {        if(MaxSize <=0) {            Throw NewIllegalArgumentException ("maxSize <= 0"); }         This. maxSize =maxSize;  This. Map =NewLinkedhashmap<k, V> (0,0.75f,true); }     PublicFinal VGet(K key) {if(Key = =NULL) {            Throw NewNullPointerException ("key = = NULL");        } V Mapvalue; Synchronized ( This) {Mapvalue= map.Get(key); if(Mapvalue! =NULL) {HitCount++;//hit                returnMapvalue; } Misscount++;//lost} V Createdvalue=Create (key); if(Createdvalue = =NULL) {            return NULL; } synchronized ( This) {Createcount++;//Create + +Mapvalue =map.put (key, Createdvalue); if(Mapvalue! =NULL) {                //There is a conflict so undo the last put//if OldValue is present, then undo put ()map.put (key, Mapvalue); } Else{size+=safesizeof (key, Createdvalue); }        }        if(Mapvalue! =NULL) {entryremoved (false, Key, Createdvalue, Mapvalue); returnMapvalue; } Else{trimtosize (maxSize); returnCreatedvalue; }    }         Publicfinal V put (K key, V value) {if(Key = =NULL|| Value = =NULL) {              Throw NewNullPointerException ("key = = NULL | | value = = NULL");          } V Previous; Synchronized ( This) {Putcount++; Size+=safesizeof (key, value); Previous=map.put (key, value); if(Previous! =NULL) {//the value of the previous value returnedSize-=safesizeof (key, previous); }          }            if(Previous! =NULL) {entryremoved (false, key, Previous, value);          } trimtosize (MaxSize); returnprevious; }      //empty the cache space    Private voidTrimToSize (intmaxSize) {           while(true) {K key;              V value; Synchronized ( This) {                  if(Size <0|| (Map.isempty () && Size! =0)) {                      Throw Newillegalstateexception (GetClass (). GetName ()+". SizeOf () is reporting inconsistent results!"); }                    if(Size <=maxSize) {                       Break; } map.entry<k, v> toevict =Map.entryset (). iterator (). Next (); if(Toevict = =NULL) {                       Break; } Key=Toevict.getkey (); Value=Toevict.getvalue ();                  Map.Remove (key); Size-=safesizeof (key, value); Evictioncount++; } entryremoved (true, key, Value,NULL); }      }      //Delete the corresponding cache entry for key and return the corresponding value     Publicfinal V Remove (K key) {if(Key = =NULL) {              Throw NewNullPointerException ("key = = NULL");          } V Previous; Synchronized ( This) {Previous=Map.Remove (key); if(Previous! =NULL) {size-=safesizeof (key, previous); }          }            if(Previous! =NULL) {entryremoved (false, Key, Previous,NULL); }            returnprevious; }      //called when item is recycled or erased.    This method is called by remove when value is reclaimed to free storage space, or when a put call is replaced with the item value, and the default implementation does nothing. //true: To free space is removed; False:put or remove causes    protected voidentryremoved (Boolean evicted, K key, v OldValue, v newvalue) {}protectedV Create (K key) {return NULL; }        Private intsafesizeof (K key, V value) {intresult =sizeOf (key, value); if(Result <0) {              Throw NewIllegalStateException ("Negative Size:"+ key +"="+value); }          returnresult; }          protected intsizeOf (K key, V value) {return 1; }    //Empty Cache     PublicFinalvoidEvictall () {trimtosize (-1);//-1 'll evict 0-sized elements    }         PublicSynchronized finalintsize () {returnsize; }         PublicSynchronized finalintmaxSize () {returnmaxSize; }         PublicSynchronized finalintHitCount () {returnHitCount; }         PublicSynchronized finalintMisscount () {returnMisscount; }         PublicSynchronized finalintCreatecount () {returnCreatecount; }         PublicSynchronized finalintPutcount () {returnPutcount; }        //returns the number of recycled     PublicSynchronized finalintEvictioncount () {returnEvictioncount; }      //returns a copy of the current cache, from the least recently accessed to the most visited     PublicSynchronized final map<k, v>Snapshot () {return NewLinkedhashmap<k, v>(map); }         PublicSynchronized Final String toString () {intAccesses = HitCount +Misscount; intHitpercent = accesses! =0? ( -* hitcount/accesses):0; returnString.Format ("lrucache[maxsize=%d,hits=%d,misses=%d,hitrate=%d%%]", MaxSize, HitCount, Misscount, hitpercent); }  }

Android LRUCache Class Analysis