Java Programming — I/O Streams Questions & Answers

Q.51 Hard I/O Streams

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

A It automatically handles encoding

B It supports memory mapping and direct buffer access

C It doesn't require closing

D It's easier to use than streams

Correct Answer: B. It supports memory mapping and direct buffer access

EXPLANATION

FileChannel supports memory-mapped files and direct buffer manipulation, enabling high-performance I/O operations not possible with traditional streams.

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Q.52 Easy I/O Streams

What happens when you attempt to read from a closed InputStream?

A Returns -1

B Throws IOException

C Returns empty byte array

D Silently ignores the read request

Correct Answer: B. Throws IOException

EXPLANATION

Attempting to read from a closed stream throws an IOException with message 'Stream closed', preventing accidental data processing from invalid sources.

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Q.53 Hard I/O Streams

For encrypting data while writing to a file, which approach is most appropriate?

A Use FileWriter directly with encoded strings

B Wrap FileOutputStream with CipherOutputStream

C Use PrintWriter with encryption library

D Convert data to hexadecimal before writing

Correct Answer: B. Wrap FileOutputStream with CipherOutputStream

EXPLANATION

CipherOutputStream allows transparent encryption of data written through it, properly integrating with Java's cryptography framework.

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Q.54 Medium I/O Streams

Which method of PushbackInputStream allows you to return bytes to the stream to be read again?

A reset()

B unread()

C rewind()

D goBack()

Correct Answer: B. unread()

EXPLANATION

The unread() method of PushbackInputStream allows you to push bytes back into the stream so they can be read again.

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Q.55 Medium I/O Streams

In a multi-threaded application, which stream class is thread-safe?

A FileInputStream

B BufferedReader

C PrintWriter

D FileOutputStream

Correct Answer: C. PrintWriter

EXPLANATION

PrintWriter is synchronized, making it thread-safe. Other stream classes are not inherently thread-safe and require external synchronization in multi-threaded contexts.

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Q.56 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.

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Q.57 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.

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Q.58 Easy I/O Streams

Which class would you use to read and write at arbitrary positions in a file?

A BufferedReader

B FileInputStream

C RandomAccessFile

D PushbackInputStream

Correct Answer: C. RandomAccessFile

EXPLANATION

RandomAccessFile allows reading and writing at arbitrary positions using seek() method, useful for direct access to file contents.

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Q.59 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.

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Q.60 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.

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