KnowledgeCheck.md

# Quiz.md

# Java Collections Framework Quiz — Collection Interface

## Instructions
Answer the following **10 questions** about the **Java `Collection` interface** and common collection methods.  
Select the **best answer** for each question.

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## Question 1
Which of the following is **true** about the `Collection` interface?

A. `Collection` is a class  
B. `Collection` extends `List`  
**C. `Collection` is the root interface for most collection types**  
D. `Collection` only stores key-value pairs  

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## Question 2
What will the following code print?

```java
Collection<Integer> numbers = new ArrayList<>();

numbers.add(10);
numbers.add(20);
numbers.add(30);

System.out.println(numbers.size());

A. 0 B. 1 C. 3 D. 30

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Question 3

Which method is used to check if an element exists inside a collection?

A. search() B. exists() C. contains() D. check()

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Question 4

What will the following code print?

Collection<String> names = new ArrayList<>();

names.add("Alex");
names.add("Jordan");

names.remove("Alex");

System.out.println(names);

A. [Alex, Jordan] B. [Jordan] C. [Alex] D. []

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Question 5

Which method adds all elements from another collection into an existing collection?

A. add() B. addAll() C. insertAll() D. merge()

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Question 6

What will the following code print?

Collection<Integer> numbers = new ArrayList<>();

System.out.println(numbers.isEmpty());

A. true B. false C. 0 D. Compilation error

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Question 7

Which method removes all elements from a collection?

A. removeAll() B. deleteAll() C. clear() D. reset()

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Question 8

What will the following code print?

Collection<Integer> nums = new ArrayList<>();

nums.add(5);
nums.add(10);
nums.add(15);

for(Integer n : nums) {
    System.out.print(n + " ");
}

A. 5 10 15 B. 15 10 5 C. 0 1 2 D. Compilation error

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Question 9

Which of the following cannot be guaranteed when using the Collection interface?

A. Elements can be added B. Elements can be removed C. Indexed access using .get(index) D. Elements can be iterated using a loop

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Question 10

What is the main benefit of writing code like this?

Collection<String> fruits = new ArrayList<>();

A. It automatically sorts the collection B. It prevents duplicates C. It allows flexibility to change implementations later D. It forces the collection to be synchronized