Consider code where Thread A holds Lock1 and waits for Lock2, while Thread B holds Lock2 and waits for Lock1. What is this scenario called?

The correct answer is C: Deadlock. This is a classic circular wait scenario resulting in deadlock, where neither thread can proceed because each is waiting for a resource held by the other.

What will be the output of reading from a ByteArrayInputStream initialized with bytes [65, 66, 67] after calling read() three times?

The correct answer is A: 65, 66, 67. read() returns integer values of bytes. [65, 66, 67] are ASCII values for 'A', 'B', 'C'. Multiple read() calls return these values sequentially.

Which of the following best describes encapsulation?

The correct answer is A: Hiding implementation details and providing controlled access through methods. Encapsulation involves bundling data (variables) and methods, hiding implementation details, and providing public methods for access. It protects data integrity.

What is the main advantage of using ExecutorService over directly creating threads?

The correct answer is B: Thread reuse and better resource management. ExecutorService manages a pool of threads, reusing them for multiple tasks, which reduces overhead and improves resource utilization.

Which interface in Java Collections Framework is used to maintain insertion order while allowing duplicates?

The correct answer is A: List. List interface maintains insertion order and allows duplicate elements. ArrayList, LinkedList, and Vector are common implementations.

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Java Programming
I/O Streams

Java OOP, collections, multithreading

53 Q 10 Topics Take Mock Test

Difficulty: All Easy Medium Hard 31–40 of 53

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.31 Medium I/O Streams

What is the default charset used by InputStreamReader if none is specified?

A UTF-8

B ISO-8859-1

C System default charset

D ASCII

Correct Answer: C. System default charset

EXPLANATION

If no charset is explicitly provided, InputStreamReader uses the platform's default charset, which varies by system configuration.

Test

Q.32 Medium I/O Streams

When processing a large XML file, which approach is most memory-efficient?

A Load entire file into memory using FileInputStream

B Use BufferedReader to read line-by-line

C Use SAX parser or streaming XML parser

D Convert file to ObjectInputStream

Correct Answer: C. Use SAX parser or streaming XML parser

EXPLANATION

SAX parsers and streaming XML parsers process XML sequentially without loading the entire document, making them ideal for large files.

Test

Q.33 Medium I/O Streams

In a real-time application processing sensor data streams, which buffering approach would minimize latency?

A Increase buffer size to 64KB

B Use unbuffered I/O or very small buffer sizes with frequent flush()

C Use ObjectInputStream for all data

D Implement custom byte arrays

Correct Answer: B. Use unbuffered I/O or very small buffer sizes with frequent flush()

EXPLANATION

For real-time applications requiring minimal latency, smaller buffer sizes and frequent flushing ensure data is processed immediately rather than waiting for buffer to fill.

Test

Q.34 Medium I/O Streams

What exception is thrown when trying to deserialize an object that was serialized with a different serialVersionUID?

A ClassCastException

B InvalidClassException

C StreamCorruptedException

D NotSerializableException

Correct Answer: B. InvalidClassException

EXPLANATION

InvalidClassException is thrown when a serialized object's serialVersionUID doesn't match the current class definition, indicating an incompatible class version.

Test

Q.35 Medium I/O Streams

A file contains 1000 lines. Using BufferedReader.readLine() repeatedly reads all lines. What is the time complexity?

A O(1)

B O(log n)

C O(n)

D O(n²)

Correct Answer: C. O(n)

EXPLANATION

Reading each line requires processing each character once, resulting in O(n) complexity where n is total characters.

Test

Q.36 Medium I/O Streams

Which scenario would require using a SequenceInputStream?

A Reading from multiple files sequentially as a single stream

B Reading very large files

C Parallel reading from multiple files

D Converting stream encoding

Correct Answer: A. Reading from multiple files sequentially as a single stream

EXPLANATION

SequenceInputStream concatenates multiple input streams, allowing them to be read as one continuous stream.

Test

Q.37 Medium I/O Streams

What happens when you write to a closed PrintWriter?

A The data is buffered and written on next open

B IOException is thrown

C Data is silently discarded

D The stream reopens automatically

Correct Answer: C. Data is silently discarded

EXPLANATION

PrintWriter suppresses IOException and continues silently, unlike other streams.

Test

Q.38 Medium I/O Streams

What is the serialVersionUID used for in Java serialization?

A To store the Java version number

B To identify the class version for deserialization compatibility

C To encrypt the serialized object

D To track the number of times an object was serialized

Correct Answer: B. To identify the class version for deserialization compatibility

EXPLANATION

serialVersionUID identifies class versions. Mismatched versions cause InvalidClassException during deserialization.

Test

Q.39 Medium I/O Streams

In a CSV file processing application, why is BufferedReader preferred over FileReader for reading large files?

A BufferedReader automatically parses CSV format

B BufferedReader reduces I/O operations by reading data in chunks

C FileReader cannot read text files

D BufferedReader is faster at character encoding

Correct Answer: B. BufferedReader reduces I/O operations by reading data in chunks

EXPLANATION

BufferedReader buffers input, reducing system calls and I/O overhead, improving performance significantly.

Test

Q.40 Medium I/O Streams

When implementing Externalizable interface, which method is mandatory?

A serialize()

B writeObject() and readObject()

C writeExternal() and readExternal()

D write() and read()

Correct Answer: C. writeExternal() and readExternal()

EXPLANATION

Externalizable requires implementation of writeExternal() and readExternal() for complete control over serialization.

Test

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