private static float[] getAndCreateEstimationIfAbsent(String topic) {
        float[] compressionRatioForTopic = COMPRESSION_RATIO.get(topic);
        if (compressionRatioForTopic == null) {
            compressionRatioForTopic = initialCompressionRatio();
            float[] existingCompressionRatio = COMPRESSION_RATIO.putIfAbsent(topic, compressionRatioForTopic);
            // Someone created the compression ratio array before us, use it.
            if (existingCompressionRatio != null)
                return existingCompressionRatio;
        }
        return compressionRatioForTopic;
    }
Set the compression estimation for a topic compression type combination. This method is for unit test purpose.
clients/src/main/java/org/apache/kafka/common/record/CompressionRatioEstimator.java