Expired collection of java

For example, Redis allows you to specify an expiration date for an entry. That's generally enough, but look for a collection library in Java that can do that.

Source code

pom.xml

	<properties>
		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
		<java.version>11</java.version>
	</properties>

	<dependencies>
		<!-- https://mvnrepository.com/artifact/org.apache.commons/commons-collections4 -->
		<dependency>
			<groupId>org.apache.commons</groupId>
			<artifactId>commons-collections4</artifactId>
			<version>4.4</version>
		</dependency>
		<!-- https://mvnrepository.com/artifact/com.google.guava/guava -->
		<dependency>
			<groupId>com.google.guava</groupId>
			<artifactId>guava</artifactId>
			<version>28.0-jre</version>
		</dependency>

	</dependencies>

Passive Expiring Map from Apache Commons Collections

import java.util.Map;
import java.util.concurrent.TimeUnit;

import org.apache.commons.collections4.map.PassiveExpiringMap;

public class App {
    public static void main(String[] args) throws InterruptedException {

        Map<String, String> map = new PassiveExpiringMap<String, String>(3000, TimeUnit.MILLISECONDS);
        map.put("key1", "value1");

        while (true) {
            TimeUnit.MILLISECONDS.sleep(1000);
            System.out.println(map.size());
        }
    }
}

When the above is executed, it becomes as follows.

1
1
0

Expiration date 3 seconds. Expiration is not checked unless you perform a specific operation on the map as `Passive`. What is a specific operation? ```All expired entries are removed from .. as shown in https://commons.apache.org/proper/commons-collections/apidocs/org/apache/commons/collections4/map/PassiveExpiringMap.html The one with .`` `or something written on it.

note that passiveexpiringmap is not synchronized and is not thread-safeIt is written that you need to be careful there.

Guava's Cache Builder

import java.util.concurrent.TimeUnit;

import com.google.common.cache.Cache;
import com.google.common.cache.CacheBuilder;

public class GuavaCaamain {

    public static void main(String[] args) throws InterruptedException {        
        Cache<String, String> cache = CacheBuilder.newBuilder().expireAfterWrite(3000, TimeUnit.MILLISECONDS).build();
        cache.put("key1", "value1");
        
        while (true) {
            TimeUnit.MILLISECONDS.sleep(1000);
            cache.put("key2", "value2");
            System.out.println(cache.size());
        }

    }

}

When the above is executed, it becomes as follows.

2
2
1

Check the expiration date at the time of writing as shown in expireAfterWrite </ code>. So if you delete the put line from the above code, the cache contents will not change.

Cache<String, String> cache = CacheBuilder.newBuilder().expireAfterAccess(3000, TimeUnit.MILLISECONDS).build();