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Java Programming

Java OOP, collections, multithreading

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Difficulty: All Easy Medium Hard 421–430 of 958

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.421 Easy I/O Streams

Which class in Java I/O streams is used to read primitive data types from a binary file?

A DataInputStream

B FileReader

C BufferedInputStream

D InputStreamReader

Correct Answer: A. DataInputStream

EXPLANATION

DataInputStream provides methods like readInt(), readDouble(), readBoolean() to read primitive data types from a binary file.

Test

Q.422 Hard I/O Streams

For a real-time log file monitoring application, which approach is most suitable?

A Use FileInputStream and reload file periodically

B Use RandomAccessFile to seek to end and read new appended data

C Use FileWatcher API for detecting changes

D Load entire file in memory and check periodically

Correct Answer: B. Use RandomAccessFile to seek to end and read new appended data

EXPLANATION

RandomAccessFile allows seeking to the file's end to read only new appended data efficiently.

Test

Q.423 Easy I/O Streams

When using ObjectInputStream, what exception is thrown if the serialVersionUID doesn't match?

A SerializationException

B InvalidClassException

C ClassNotFoundException

D IOException

Correct Answer: B. InvalidClassException

EXPLANATION

InvalidClassException is thrown when deserialized class's serialVersionUID doesn't match the serialized object.

Test

Q.424 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.425 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.426 Hard I/O Streams

In Java NIO, what is the primary advantage of FileChannel over traditional streams?

A FileChannel is easier to use

B FileChannel supports non-blocking I/O and memory-mapped files

C FileChannel automatically handles buffering

D FileChannel is compatible with older Java versions

Correct Answer: B. FileChannel supports non-blocking I/O and memory-mapped files

EXPLANATION

FileChannel enables non-blocking operations and memory-mapping, offering better performance for large files.

Test

Q.427 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.428 Hard I/O Streams

A program reads a 1 GB binary file and needs to modify specific bytes at random positions. Which class is most suitable?

A BufferedInputStream with ByteArrayOutputStream

B FileInputStream with external byte array

C RandomAccessFile

D FileInputStream wrapped with DataInputStream

Correct Answer: C. RandomAccessFile

EXPLANATION

RandomAccessFile allows seeking to any position in the file without sequential reading, ideal for random access.

Test

Q.429 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.430 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

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