Java without Java Collection is really hard to imagine. I spend almost couple of hours a day working on Java Projects for my clients.
HashMap, Map, Static Objects, Java Interface are the most commonly used terms.
Sometime back I’ve written an article on How to remove elements from HashMap Automatically using Java Timer and Futures Object?
In this tutorial, we will go over similar concept but not using Timer but ExpiringMap 
java – Map with automatically expiring elements
Let’s get started:
Step-1.
Create Java Class CrunchifyNetJodahExpiringMapExample.java.
Step-2.
Add Maven net.jodah.expiringmap Dependency.
If you don’t see pom.xml file into your Eclipse Environment then follow this steps.
<dependency>
<groupId>net.jodah</groupId>
<artifactId>expiringmap</artifactId>
<version>0.5.7</version>
</dependency>
Step-3
Create object curnchifyMap with Expiration time set to 5 seconds.
Step-4
- Add an element to
crunchifyMapevery second - We will also print the number of element for that map using
size()method
Step-5
As you will see in Output, there will not be more than 5 elements over 5 seconds into crunchifyMap.
Complete Java Example:
package crunchify.com.tutorial;
import java.util.Map;
import java.util.concurrent.TimeUnit;
import net.jodah.expiringmap.ExpiringMap;
/**
* @author Crunchify.com
*
* - ExpiringMap is a high performance, thread-safe ConcurrentMap implementation that expires entries.
* - Ideally no performance overhead without any external dependency
*
*/
public class CrunchifyNetJodahExpiringMapExample {
// Create Exipring Map called crunchifyMap with expiry time 5 seconds
private static Map<String, Double> crunchifyMap = ExpiringMap.builder().expiration(5, TimeUnit.SECONDS).build();
public static void main(String[] args) {
{
// Let's keep running loop for testing
while (true) {
try {
// Just wait for a second everytime
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
// Add Element to Map crunchifyMap
addElement();
// Print Element to Map crunchifyMap
printElement();
}
}
}
private static void printElement() {
log("crunchifyMap Size: " + crunchifyMap.size() + "\n");
}
// NOTE: We are adding Unique Element to Map Every time.
private static void addElement() {
double randomValue = Math.random();
// If the specified key is not already associated with a value (or is mapped to null) associates it with the
// given value and returns null, else returns the current value.
crunchifyMap.putIfAbsent("Crunchify " + randomValue, randomValue);
log("+++++ Element added to crunchifyMap:" + randomValue);
}
private static void log(String string) {
System.out.println(string);
}
}
Console Output:
+++++ Element added to crunchifyMap:0.217495756642075 crunchifyMap Size: 1 +++++ Element added to crunchifyMap:0.3848009195646136 crunchifyMap Size: 2 +++++ Element added to crunchifyMap:0.7844845177791825 crunchifyMap Size: 3 +++++ Element added to crunchifyMap:0.19386945925964516 crunchifyMap Size: 4 +++++ Element added to crunchifyMap:0.7279066292650116 crunchifyMap Size: 5 +++++ Element added to crunchifyMap:0.6664624769347492 crunchifyMap Size: 5 <========== check this: map size fixed to 5 as element expires every 1 seconds too +++++ Element added to crunchifyMap:0.8867273405922911 crunchifyMap Size: 5 +++++ Element added to crunchifyMap:0.06620783012520237 crunchifyMap Size: 5
The post How to use net.jodah.ExpiringMap Maven Java Utility to Remove Expired Objects from HashMap Automatically – Complete Java Tutorial appeared first on Crunchify.
Author: App Shah
