Caffeine: size based eviction

Caffeine evict the items when the configured size limit of the cache is exceeded.

 

Example

Cache<Integer, Employee> cache = Caffeine.newBuilder().initialCapacity(1).maximumSize(2).expireAfterWrite(30, TimeUnit.SECONDS).build();

 

As you see above snippet, I set the maximum cache size to 2, when you try to insert 3^rd item to the cache, the least recently used record is deleted from the cache.

 

Find the below working application.

 

Employee.java

package com.sample.app.model;

public class Employee {

	private int id;
	private String firstName;
	private String lastName;

	public Employee(int id, String firstName, String lastName) {
		super();
		this.id = id;
		this.firstName = firstName;
		this.lastName = lastName;
	}

	public int getId() {
		return id;
	}

	public void setId(int id) {
		this.id = id;
	}

	public String getFirstName() {
		return firstName;
	}

	public void setFirstName(String firstName) {
		this.firstName = firstName;
	}

	public String getLastName() {
		return lastName;
	}

	public void setLastName(String lastName) {
		this.lastName = lastName;
	}

	@Override
	public String toString() {
		return "Employee [id=" + id + ", firstName=" + firstName + ", lastName=" + lastName + "]";
	}

}

 

App.java

package com.sample.app;

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

import com.github.benmanes.caffeine.cache.Cache;
import com.github.benmanes.caffeine.cache.Caffeine;
import com.sample.app.model.Employee;

public class App {
	
	private static void printCache(Cache cache) {
		System.out.println("\n\nElements of cache are");
		Map map = cache.asMap();
		
		for(Object key : map.keySet()) {
			System.out.println(map.get(key));
		}
	}

	public static void main(String args[]) throws InterruptedException {
		Cache<Integer, Employee> cache = Caffeine.newBuilder().initialCapacity(1).maximumSize(2)
				.expireAfterWrite(30, TimeUnit.SECONDS).build();

		TimeUnit.SECONDS.sleep(2);

		Employee emp1 = new Employee(1, "Krishna", "Gurram");
		Employee emp2 = new Employee(2, "Gopi", "Battu");
		Employee emp3 = new Employee(3, "Saurav", "Sarkar");

		cache.put(emp1.getId(), emp1);
		cache.put(emp2.getId(), emp2);
		cache.put(emp3.getId(), emp3);
		
		printCache(cache);

		long estimatedSize = cache.estimatedSize();
		System.out.println("Estimated number of elements in the cache : " + estimatedSize);

		/*
		 * Since cache eviction is done asynchronously, let's execute pending
		 * maintenance operations needed by the cache
		 */
		System.out.println("\nPerforming cleanup operations\n");
		cache.cleanUp();
		
		printCache(cache);

		estimatedSize = cache.estimatedSize();
		System.out.println("Estimated number of elements in the cache : " + estimatedSize);
	}

}

 

Output

Elements of cache are
Employee [id=1, firstName=Krishna, lastName=Gurram]
Employee [id=2, firstName=Gopi, lastName=Battu]
Employee [id=3, firstName=Saurav, lastName=Sarkar]
Estimated number of elements in the cache : 2

Performing cleanup operations



Elements of cache are
Employee [id=2, firstName=Gopi, lastName=Battu]
Employee [id=3, firstName=Saurav, lastName=Sarkar]
Estimated number of elements in the cache : 2

 

 

 

 

  

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