android缓存机制

一般android会采用缓存机制，内存缓存采用LruCache，存储缓存采用DiskLruCache
LruCache内部维护了一个LinkedHashMap

 /**     * @param maxSize for caches that do not override {@link #sizeOf}, this is     *     the maximum number of entries in the cache. For all other caches,     *     this is the maximum sum of the sizes of the entries in this cache.     */    public LruCache(int maxSize) {        if (maxSize <= 0) {            throw new IllegalArgumentException("maxSize <= 0");        }        this.maxSize = maxSize;        this.map = new LinkedHashMap(0, 0.75f, true);    }

同时是线程安全的

   synchronized (this) {            mapValue = map.get(key);            if (mapValue != null) {                hitCount++;                return mapValue;            }            missCount++;        }   synchronized (this) {            createCount++;            mapValue = map.put(key, createdValue);            if (mapValue != null) {                // There was a conflict so undo that last put                map.put(key, mapValue);            } else {                size += safeSizeOf(key, createdValue);            }        }

一般存储空间为当前运行空间的1／8 单位为KB
LruCache 3.1以后源码可见
DiskLruCache 一般存储空间为50M key采用url经过Md5加密，防止url中的特殊字符，value为bitmap，对外提供get，put方法

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