Introduction to Java Generics

1. What are Generics?

Generics in Java allow you to define classes, interfaces, and methods with a placeholder for types, enabling type safety and reducing code duplication.

2. Benefits of Generics

• Type Safety: Catch errors at compile-time rather than at runtime.
• Code Reusability: Write a single method or class to handle various types.
• Elimination of Casts: Reduces the need for casting when retrieving values.

3. Basic Syntax

Generics are defined using angle brackets (<>). Here’s how you can create a simple generic class:

public class Box<T> {
    private T item;

    public void setItem(T item) {
        this.item = item;
    }

    public T getItem() {
        return item;
    }
}
            

4. Wildcards

Wildcards are represented by ? and allow for flexibility in your generics. They can be bounded or unbounded:

public void printBox(Box<? extends Number> box) {
    System.out.println(box.getItem());
}
            

5. Best Practices

Follow these best practices when working with Java Generics:

1. Use descriptive type parameters (e.g., <E> for elements, <K,V> for key-value pairs).
2. Prefer using bounded wildcards when you need to read from a data structure.
3. Avoid using raw types; always use parameterized types for type safety.

6. FAQ