やる気ない感じのランダムゆらぎの実装 with Java and Caffeine

CaffeineTest.java

import java.security.SecureRandom;
import java.util.Random;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import javax.annotation.Nonnull;

import lombok.RequiredArgsConstructor;
import lombok.extern.slf4j.Slf4j;

import org.junit.Test;

import com.github.benmanes.caffeine.cache.Cache;
import com.github.benmanes.caffeine.cache.Caffeine;
import com.github.benmanes.caffeine.cache.Expiry;

@Slf4j
public class CaffeineTest {
	
	@Test
	public void test() throws InterruptedException {
		Cache<Object, Object> cache = Caffeine.newBuilder()
			.maximumSize(1000)
			.expireAfter(new MyExpiry<>(new MyDurationGenerator<>()))
			.removalListener((key, value, cause) -> log.info("expired {}: {}", key, cause))
			.build();
		
		Function<Object, Object> read = o -> {
			log.info("reading...");
			return o;
		};
		
		log.info("read1");
		cache.get("test", read);
		Thread.sleep(2000);
		log.info("read2");
		cache.get("test", read);
		log.info("read3");
		cache.get("test", read);
		log.info("read4");
		cache.get("test", read);
		
	}
	
	@RequiredArgsConstructor
	static class MyExpiry<K, V> implements Expiry<K, V> {
		
		private final DurationGenerator<K, V> generator;
		
		@Override
		public long expireAfterCreate(@Nonnull K key, @Nonnull V value, long currentTime) {
			return generator.generate(key, value, currentTime);
		}
		
		@Override
		public long expireAfterUpdate(@Nonnull K key, @Nonnull V value, long currentTime,
			long currentDuration) {
			return currentDuration;
		}
		
		@Override
		public long expireAfterRead(@Nonnull K key, @Nonnull V value, long currentTime,
			long currentDuration) {
			return currentDuration;
		}
	}
	
	interface DurationGenerator<K, V> {
		
		long generate(@Nonnull K key, @Nonnull V value, long currentTime);
		
	}
	
	class MyDurationGenerator<K, V> implements DurationGenerator<K, V>{
		
		private final Random rand = new SecureRandom();
		
		private final long base = TimeUnit.NANOSECONDS.convert(10, TimeUnit.MINUTES) / 2;
		
		@Override
		public long generate(@Nonnull K key, @Nonnull V value, long currentTime) {
			return (long) (base + 2 * base * rand.nextDouble()); // [base, 3 * base]
		}
	}
}