OCP OCP Java IO and NIO 1 — Questions and Answers
Question 1: Which Java class is designed specifically to read character data from a file using a character stream?
- FileInputStream
- FileReader (Correct answer)
- BufferedInputStream
- DataInputStream
Correct answer: FileReader
FileReader is a character stream (Reader subclass) that reads text data from a file, while FileInputStream reads raw bytes.
Question 2: What is the primary benefit of wrapping a FileWriter with a BufferedWriter in Java?
- It compresses data before writing to the file
- It reduces the number of actual write operations through internal buffering (Correct answer)
- It enables writing to multiple files simultaneously
- It automatically flushes on each write call
Correct answer: It reduces the number of actual write operations through internal buffering
BufferedWriter wraps another Writer with an internal buffer, batching multiple small writes into fewer, more efficient I/O operations.
Question 3: What exception type must be handled or declared when performing file I/O operations in Java?
- RuntimeException
- IOException (Correct answer)
- FileException
- StreamException
Correct answer: IOException
IOException is a checked exception that is the parent of all I/O-related exceptions and must be handled with try-catch or declared in the method signature.
Question 4: Which Java I/O class provides methods like readInt() and readDouble() to read primitive data types from a binary file?
- FileReader
- ObjectInputStream
- DataInputStream (Correct answer)
- RandomAccessFile
Correct answer: DataInputStream
DataInputStream wraps an InputStream and adds typed read methods for all Java primitive data types, making binary file parsing straightforward.
Question 5: What guarantee does the Java try-with-resources statement provide when used with I/O streams?
- Streams are opened only once per program run
- Streams are automatically closed when the try block exits (Correct answer)
- Exceptions thrown inside streams are always suppressed
- Streams are flushed to disk before the block exits
Correct answer: Streams are automatically closed when the try block exits
Try-with-resources automatically invokes close() on any AutoCloseable resource declared in the try header when the block completes, normally or exceptionally.
Question 6: Which method of the java.io.File class returns true if the file or directory at the specified path exists on the file system?
- isPresent()
- exists() (Correct answer)
- checkExists()
- fileFound()
Correct answer: exists()
The exists() method of java.io.File returns true if the abstract pathname denotes an existing file or directory on the filesystem.
OCP OCP Java IO and NIO 1
Which Java class is designed specifically to read character data from a file using a character stream?