Groovy and Grails Groovy Language Fundamentals & Metaprogramming

Question 1

In Groovy, what does the `?.` operator do?

Accepted Answer

Safely navigates null references, returning null instead of throwing NullPointerException

Answer

Performs a strict equality check

Answer

Declares an optional method parameter

Answer

Casts an object to a nullable type

Question 2

Which of the following correctly defines a Groovy closure that accepts two parameters and returns their sum?

Accepted Answer

def sum = { a, b -> a + b }

Answer

def sum = (a, b) -> a + b

Answer

def sum = closure(a, b) { a + b }

Answer

def sum = [a, b] { return a + b }

Question 3

What is the implicit variable name for the single parameter of a Groovy closure when no parameter is declared?

Accepted Answer

it

Answer

self

Answer

arg

Answer

param

Question 4

In Groovy, what is the result of `[1, 2, 3].collect { it * 2 }`?

Accepted Answer

[2, 4, 6]

Answer

6

Answer

[1, 4, 9]

Answer

null

Question 5

Which Groovy GDK method filters a list and returns only elements that match a condition?

Accepted Answer

findAll

Answer

collect

Answer

inject

Answer

each

Question 6

What does the Groovy `def` keyword indicate when used for a variable declaration?

Accepted Answer

The variable is dynamically typed and can hold any value

Answer

The variable is final and cannot be reassigned

Answer

The variable is statically typed as Object

Answer

The variable is private to the current class

Question 7

What is the output of the following Groovy code: `println 'Hello' * 3`?

Accepted Answer

HelloHelloHello

Answer

Hello3

Answer

3Hello

Answer

Compilation error