Java Generics, Enums, and Autoboxing Flashcards

What does `Collections.emptyList()` return and why is it preferred?

Answer: An immutable, type-safe empty List singleton

`Collections.emptyList()` returns a shared, immutable, type-safe empty List, avoiding null checks and unnecessary object creation.

What is the `ordinal()` method in a Java enum?

Answer: Returns the zero-based position of the constant in the enum declaration

`ordinal()` returns the position of the enum constant in its declaration order, starting from 0.

Which of the following statements about Java generics and arrays is true?

Answer: Generic arrays cannot be created directly due to type erasure

You cannot directly create generic arrays (`new T[10]`) because type erasure removes the type information needed for array creation at runtime.

What is the purpose of the `@SuppressWarnings("unchecked")` annotation in Java?

Answer: To suppress compiler warnings about unchecked or unsafe generic operations

`@SuppressWarnings("unchecked")` tells the compiler to suppress warnings generated by unchecked casts or raw type usage in generics.

In Java, which method retrieves an enum constant by its name string?

Answer: EnumType.valueOf(name)

`EnumType.valueOf("CONSTANT_NAME")` returns the enum constant with the specified name, throwing `IllegalArgumentException` if not found.

What is the effect of assigning an `int` to an `Integer` variable in Java?

Answer: Autoboxing converts the int to an Integer automatically

Autoboxing automatically converts the primitive `int` to an `Integer` wrapper object when assigned to an `Integer` variable.