Implement custom eviction policy

[fmnoise]

cache = Caffeine.newBuilder().expireAfter(new Expiry<String, DataObject>() {
    @Override
    public long expireAfterCreate(
      String key, DataObject value, long currentTime) {
        return value.getData().length() * 1000;
    }
    @Override
    public long expireAfterUpdate(
      String key, DataObject value, long currentTime, long currentDuration) {
        return currentDuration;
    }
    @Override
    public long expireAfterRead(
      String key, DataObject value, long currentTime, long currentDuration) {
        return currentDuration;
    }
}).build(k -> DataObject.get("Data for " + k));