private boolean journalRebuildRequired() {
        final int REDUNDANT_OP_COMPACT_THRESHOLD = 2000;
        return redundantOpCount >= REDUNDANT_OP_COMPACT_THRESHOLD
                && redundantOpCount >= lruEntries.size();
    }
We only rebuild the journal when it will halve the size of the journal
and eliminate at least 2000 ops.
app/src/main/java/com/duan/musicoco/cache/DiskLruCache.java