Mastering Java Collections Framework

What is the primary purpose of the List interface in Java?

• To create a fixed-size array of elements.

• To provide a collection that only allows unique elements.

• To provide an ordered collection that allows for dynamic resizing and indexed access to elements.

• To manage key-value pairs in a collection.

Which class is a common implementation of the List interface?

• arrays

• HashSet

• HashMap

• ArrayList

How does a Set differ from a List?

• A Set maintains the order of elements, while a List does not.

• A Set can contain duplicates, while a List cannot.

• A Set ensures all elements are unique, while a List can have duplicates.

• A Set allows for indexed access to elements, while a List does not.

What is the main characteristic of a HashSet?

• It maintains the order of elements.

• It does not allow duplicate elements.

• It can store null values as duplicates.

• It allows duplicate elements.

What is the primary use of the Map interface in Java?

• To manage user sessions.

• To store key-value pairs.

• To handle file input/output.

• To execute SQL queries.

How do you retrieve a value from a Map using a key?

• Use map.get(key) to retrieve the value.

• map[key] returns the value directly.

• Use map.retrieve(key) to get the value.

• Call map.value(key) to access the value.

What is the difference between HashMap and TreeMap?

• HashMap does not allow nulls; TreeMap allows null keys and is unordered.

• HashMap is unordered and allows nulls; TreeMap is ordered and does not allow null keys.

• HashMap is ordered and allows null keys; TreeMap is unordered and does not allow nulls.

• HashMap is slower than TreeMap; TreeMap is faster for lookups.

What utility class provides static methods for working with collections?

• Collections

• Lists

• Sets

• Arrays

What are generics in Java?

• Generics in Java enable type-safe data structures and methods by allowing the specification of type parameters.

• Generics in Java are a way to create user interfaces.

• Generics in Java are a type of exception handling.

• Generics in Java are used for memory management.

What is the syntax for declaring a generic class in Java?

• class Order {}

• class Order[] {}

• class Order<?>{}

• class Order<T> {}