private long countTotalSize(List<File> files) {
        long totalSize = 0;
        for (File file : files) {
            totalSize += file.length();
        }
        return totalSize;
    }
{@link DiskUsage} that uses LRU (Least Recently Used) strategy to trim cache.
VideoCache/src/main/java/com/yc/videocache/file/LruDiskUsage.java