Generics Fundamentals & Type-Safe Containers (<T>)

1Concept

Generics provide compile-time type safety, allowing classes, interfaces, and methods to operate on parameterized types. They eliminate the need for manual type casting and prevent `ClassCastException` at runtime.

2Architecture Diagram

Raw Type:   List list = new ArrayList();   list.add("text"); (Integer) list.get(0); ---> ClassCastException at runtime!
Generic:    List<String> list = new ...;   list.add(10); ---> Compile Error caught immediately!

3Code Example

public class GenericsDemo {
    static class Box<T> {
        private T content;
        public void set(T content) { this.content = content; }
        public T get() { return content; }
    }

    public static void main(String[] args) {
        Box<String> stringBox = new Box<>();
        stringBox.set("Type Safe Architecture");
        String value = stringBox.get(); // Zero casting required!

        Box<Integer> intBox = new Box<>();
        intBox.set(2026);
        int year = intBox.get();

        System.out.println("StringBox: " + value);
        System.out.println("IntBox:    " + year);
    }
}

4Expected Output

StringBox: Type Safe Architecture
IntBox:    2026

5Key Takeaways

• ✓Type arguments must be reference types (`Integer`, `Double`), not primitives (`int`, `double`).
• ✓Generics provide compile-time safety and self-documenting code APIs.
• ✓Diamond operator `<>` allows compiler type argument inference.