private void trimToSize() throws IOException {
        while (size > maxSize) {
//            Map.Entry<String, Entry> toEvict = lruEntries.eldest();
            final Map.Entry<String, Entry> toEvict = lruEntries.entrySet().iterator().next();
            remove(toEvict.getKey());
        }
    }
Closes this cache. Stored values will remain on the filesystem.
app/src/main/java/com/duan/musicoco/cache/DiskLruCache.java