TtlMap - Time-to-live Map

TtlMap.java

import java.util.HashMap;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

/**
 * Time-to-live map.
 * <p>
 * Items have a specified amount of time to be accessed before they are removed.
 * Verification is done on get. Time to live is specified on map creation.
 * <p>
 * https://stackoverflow.com/questions/20827166/destroy-the-object-in-java-after-certain-time
 * 
 * @since Nov 23, 2016
 * @author Ulisses Lima
 */
@SuppressWarnings("unchecked")
public class TtlMap<K, V> {
	private Function<Long, Boolean> isAlive = (deathTime) -> deathTime - System.currentTimeMillis() > 0;

	private HashMap<K, Object[]> cache = new HashMap<>();
	private final long ttl;

	/**
	 * @param ttl time to live (in millis)
	 * @since 7 de out de 2019
	 */
	public TtlMap(long ttl) {
		this.ttl = ttl;
	}

	/**
	 * @param key
	 * @param val
	 * @since 7 de out de 2019
	 * @author Ulisses Lima
	 */
	public void put(K key, V val) {
		long deathTime = System.currentTimeMillis() + ttl;
		if (key == null)
			throw new RuntimeException("Key cannot be null!");

		cache.put(key, new Object[] { val, deathTime });
	}

	/**
	 * @param key
	 * @return value or null
	 * @since 7 de out de 2019
	 * @author Ulisses Lima
	 */
	public V get(K key) {
		if (cache.containsKey(key)) {
			Long deathTime = (Long) cache.get(key)[1];
			if (isAlive.apply(deathTime)) {
				return (V) cache.get(key)[0];
			} else {
				remove(key);
			}
		}
		return null;
	}

	/**
	 * @param key
	 * @return true if removed
	 * @since 7 de out de 2019
	 * @author Ulisses Lima
	 */
	public boolean remove(K key) {
		return removeAndGet(key) != null;
	}

	/**
	 * @param key
	 * @return value if exists
	 * @since 7 de out de 2019
	 * @author Ulisses Lima
	 */
	public V removeAndGet(Object key) {
		Object[] entry = cache.remove(key);
		if (entry != null) {
			return (V) entry[0];
		}
		return null;
	}

	public static void main(String[] args) throws InterruptedException {
		if (args.length < 1)
			throw new IllegalArgumentException("first arg must be the ttl");

		long ttl = TimeUnit.SECONDS.toMillis(Integer.valueOf(args[0]));

		TtlMap<String, String> cache = new TtlMap<String, String>(ttl);
		String key1 = "test 1";
		String key2 = "test 2";

		String val1 = "value1";
		String val2 = "value2";

		cache.put(key1, val1);
		cache.put(key2, val2);

		String x = cache.get(key1);
		if (val1.equals(x)) {
			System.out.println(key1 + ": ok");
		} else {
			System.out.println(key1 + ": fail");
		}

		x = cache.get(key2);
		if (val2.equals(x)) {
			System.out.println(key2 + ": ok");
		} else {
			System.out.println(key2 + ": fail");
		}

		Thread.sleep(ttl);

		x = cache.get(key1);
		if (x == null) {
			System.out.println(key1 + ", death: ok");
		} else {
			System.out.println(key1 + ", death: fail");
		}

		x = cache.get(key2);
		if (x == null) {
			System.out.println(key2 + ", death: ok");
		} else {
			System.out.println(key2 + ", death: fail");
		}
	}
}