In Java NIO, what is a key advantage of FileChannel over traditional I/O streams?

The correct answer is B: It supports memory mapping and direct buffer access. FileChannel supports memory-mapped files and direct buffer manipulation, enabling high-performance I/O operations not possible with traditional streams.

What does the volatile keyword guarantee in Java multithreading?

The correct answer is A: Visibility of changes across threads, but not atomicity. volatile ensures that all threads see the most recent value of a variable (visibility) but does not provide atomicity for compound operations.

Which generic wildcard usage follows the consumer pattern correctly?

The correct answer is B: public void consume(List. Consumer pattern uses '? super T' (lower bound). This allows adding elements safely. Option A (producer pattern) only allows reading, and Options C and D restrict type flexibility.

What does the available() method in InputStream return?

The correct answer is A: Number of bytes that can be read without blocking. available() returns an estimate of bytes that can be read without blocking. It doesn't return total file size.

Which of the following is the correct syntax for a multi-line comment in Java?

The correct answer is B: /* This is a comment */. Multi-line comments in Java use /* */ syntax. Single-line comments use //. Other syntaxes are for different languages.

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Java Programming
Collections Framework

Java OOP, collections, multithreading

22 Q 10 Topics Take Mock Test

Difficulty: All Easy Medium Hard 21–22 of 22

Topics in Java Programming

All Basics & Syntax 100 OOP in Java 100 Collections Framework 100 Multithreading 100 Exception Handling 100 I/O Streams 100 JDBC 100 Generics 100 Lambda Expressions 100 Spring Framework Basics 58

Q.21 Hard Collections Framework

What is the initial capacity and growth strategy of ArrayList?

A Initial capacity 10, grows by 50%

B Initial capacity 16, grows by 100%

C Initial capacity 10, grows by 100% (1.5x from Java 9)

D Initial capacity 5, grows by 25%

Correct Answer: C. Initial capacity 10, grows by 100% (1.5x from Java 9)

EXPLANATION

ArrayList starts with capacity 10. Growth factor is 50% + 1 in older versions, and 1.5x from Java 9 onwards.

Test

Q.22 Hard Collections Framework

Which method throws ConcurrentModificationException when collection is modified during iteration?

A Iterator.next()

B Enhanced for loop only

C Both Iterator and enhanced for loop

D Collection.remove()

Correct Answer: C. Both Iterator and enhanced for loop

EXPLANATION

Both Iterator and enhanced for loop use fail-fast mechanism and throw ConcurrentModificationException if collection is modified during iteration.

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Collections Framework