Java Generics, Enums, and Autoboxing Flashcards

What is the primary benefit of using generics in Java?

Answer: Type safety at compile time, eliminating the need for explicit casting

Generics allow type parameters to be specified at compile time, catching type errors early and eliminating the need for unsafe casts.

What is type erasure in Java generics?

Answer: Removing type parameter information at compile time so the bytecode uses raw types

Java implements generics through type erasure: type parameters are removed at compile time and replaced with their bounds (or Object), so no generic type info exists at runtime.

What does autoboxing in Java do?

Answer: Automatically converts primitive types to their wrapper class equivalents

Autoboxing is the automatic conversion of primitives (like `int`) to their wrapper classes (like `Integer`) when needed by the context.

Which of the following correctly declares a generic method in Java?

Answer: public T swap(T a, T b)

A generic method declares its type parameter `` before the return type: `public T methodName(...)`.

What is an enum in Java?

Answer: A special class that represents a group of named constants

An `enum` is a special Java class that defines a fixed set of named constants, with the ability to have fields, methods, and constructors.

What is the result of unboxing a null Integer in Java?

Answer: Throws NullPointerException

Unboxing a null wrapper (e.g., `Integer i = null; int x = i;`) throws a `NullPointerException` because null cannot be converted to a primitive.