The Object Pool Pattern is a design pattern that used to manage the reuse of objects in a way that can improve performance and resource utilization. This pattern is particularly useful when dealing with the creation and destruction of objects that are resource-intensive or time-consuming to instantiate. By reusing objects, you can decrease the overhead related with visit question creation and rubbish collection.

Here’s an outline of how the Object Pool Pattern works in Java:

1. Poolable Object: The objects that will be reused must adhere to a certain protocol to be managed by the pool. These objects are typically reset to a default state when they are returned to the pool so they can be reused cleanly.

2. Object Pool: This is the main class that manages the pool of reusable objects. It provides methods to borrow and return objects from the pool.

Steps to Implement Object Pool Pattern

1. Define the Poolable Object Interface: This interface ensures that the objects can be reset to a default state.

public interface Poolable {
void reset();
}

2. Implement the Poolable Object: Create the concrete class that implements the Poolable interface.

public class ReusableObject implements Poolable {
private String state;

public ReusableObject() {
// Initialization
}

@Override
public void reset() {
state = null; // Reset to default state
}

// Other methods…
}

3. Create the Object Pool: This class manages the pool of reusable objects.

import java.util.Queue;
import java.util.LinkedList;

public class ObjectPool<T extends Poolable> {
private Queue<T> availableObjects;
private int maxPoolSize;

public ObjectPool(int maxPoolSize) {
this.maxPoolSize = maxPoolSize;
this.availableObjects = new LinkedList<>();
}

protected T createNew() {
// Subclasses should override this method to create new objects
return null;
}

public synchronized T borrowObject() {
T object;
if (availableObjects.isEmpty()) {
object = createNew();
} else {
object = availableObjects.poll();
}
return object;
}

public synchronized void returnObject(T object) {
if (object != null) {
object.reset();
if (availableObjects.size() < maxPoolSize) {
availableObjects.offer(object);
}
}
}
}

4. Implement a Specific Object Pool: Extend the ObjectPool class to handle specific types of poolable objects.

public class ReusableObjectPool extends ObjectPool<ReusableObject> {

public ReusableObjectPool(int maxPoolSize) {
super(maxPoolSize);
}

@Override
protected ReusableObject createNew() {
return new ReusableObject();
}
}

5. Using the Object Pool: Finally, use the object pool in your application.

public class ObjectPoolExample {
public static void main(String[] args) {
ReusableObjectPool pool = new ReusableObjectPool(10);

// Borrow an object from the pool
ReusableObject obj1 = pool.borrowObject();

// Use the object
// …

// Return the object to the pool
pool.returnObject(obj1);

// Borrow another object
ReusableObject obj2 = pool.borrowObject();

// Use the object
// …

// Return the object to the pool
pool.returnObject(obj2);
}
}

Points to be remembered:

– Thread Safety: Ensure the object pool is thread-safe if it is accessed by multiple threads. This can be achieved by synchronizing the borrow and return methods or using concurrent collections.
– Object State: Always reset the state of the objects before returning them to the pool to avoid unexpected behavior when the objects are reused.
– Size Management: Manage the size of the pool to avoid excessive memory usage. You can set a maximum pool size and implement eviction policies if necessary.

The Object Pool Pattern can significantly improve the performance of applications that frequently create and destroy objects, especially when those objects are resource-intensive.

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Author: Ambarish Durani

JAVA Trainer

IT Education Centre Placement & Training Institute

Object Pool Design Pattern