How to Use Generic Class References in Java?

What are generic class references in Java and how can they be used?

// Example of a generic class
class Box<T> {
    private T item;
    
    public void addItem(T item) {
        this.item = item;
    }
    
    public T getItem() {
        return item;
    }
}

In Java, generics allow you to create classes, interfaces, and methods with a placeholder for the type of data they store or manipulate. This enhances code reusability, safety, and readability.

// Creating a Box for Integer type
Box<Integer> intBox = new Box<>();
intBox.addItem(10);
Integer item = intBox.getItem(); // No cast needed

Causes

• The need for type safety in collections to prevent ClassCastException.
• Code reusability without the overhead of casting objects to specific types.

Solutions

• Define a generic class by specifying a type parameter enclosed in angle brackets, e.g., <T> for type T. The type parameter can be replaced with any object type when the class is instantiated.
• Use generic types in method definitions to allow for type-safe operations on various data types.

Mistake: Mixing raw types with generic types, which can lead to warnings and unsafe operations.

Solution: Always use the generic type to ensure type safety.

Mistake: Not correctly specifying the type parameter while instantiating a generic class, leading to type mismatch errors.

Solution: Always provide the specific type when creating instances of generic classes.