Custom collection classes in Java collection framework

In the Java collection framework, we can create custom collection classes to meet specific needs. These collection classes can be created by extending the Collection interface or its sub-interfaces and need to implement all required methods, such as adding and removing elements. Custom collection classes provide fine-grained control over collection behavior, enhancing code maintainability and reusability.

Custom collection class in Java collection framework

In Java collection framework, we can create our own custom collection class as needed. Custom collection classes allow us to define collections that meet specific requirements and behaviors.

Steps

To create a custom collection class, perform the following steps:

1. Create the base class: Extend Collection Interface or its sub-interface (e.g. List, Set).
2. Implement required methods: Implement all required methods defined in the interface (such as add(), remove(), contains()).
3. Provide a builder: (Optional) Provide a builder to simplify the creation of the collection.

Practical case: car dealer collection

The following is an example of a car dealer collection, which inherits from the List interface:

import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;

public class CarDealerList implements List<Car> {

    private List<Car> cars;

    public CarDealerList() {
        cars = new ArrayList<>();
    }

    public CarDealerList(Collection<Car> cars) {
        this.cars = new ArrayList<>(cars);
    }

    // ...省略其他方法...

}

We can use this custom collection to manage cars in car dealerships:

CarDealerList cars = new CarDealerList();
cars.add(new Car("Toyota", "Camry"));
cars.add(new Car("Honda", "Civic"));

for (Car car : cars) {
    System.out.println(car);
}

Output:

Toyota Camry
Honda Civic

Advantages

The advantages of using a custom collection class include:

• Allows us to define collections that meet specific requirements.
• Provides finer control over collection operations.
• Promote code maintainability and reusability.

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