Client-Server Model & Java Streams
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Questions and Answers

What does the java.io.Reader class primarily do?

  • Flushes data to the console.
  • Writes bytes to an output stream.
  • Converts characters to bytes.
  • Reads characters from a character stream. (correct)

    • Which method in the Writer class is used to write a single character?

  • writeSignature()
  • write(int c) (correct)
  • writeChar()
  • writeElement()

    • What is the purpose of the flush() method in the Writer class?

  • To read data from a character stream.
  • To skip characters in the stream.
  • To close the stream.
  • To ensure all data is written out. (correct)

    • What advantage does BufferReader provide over simple reading methods?

    <p>It retrieves text from a buffer for efficiency.</p> Signup and view all the answers

    How does the InputStreamReader handle data?

    <p>It reads bytes and converts them into characters.</p> Signup and view all the answers

    Which method allows the Reader class to determine if it can read data without blocking?

    <p>ready()</p> Signup and view all the answers

    Which method in the Reader class skips over a specified number of characters?

    <p>skip(long n)</p> Signup and view all the answers

    What type of streams do the FileReader and FileWriter classes work with?

    <p>Character streams for text files.</p> Signup and view all the answers

    What is the primary role of a server in relation to clients?

    <p>Offers a service to clients that connect to it</p> Signup and view all the answers

    Which method is used to forcibly write any buffered data in an output stream?

    <p>flush()</p> Signup and view all the answers

    What happens if a stream is not closed in a long-running program?

    <p>Resource leaks such as open file handles may occur</p> Signup and view all the answers

    What is indicated by returning -1 from a read() method on an input stream?

    <p>The end of the stream has been reached</p> Signup and view all the answers

    What is the main advantage of using readers and writers in Java I/O?

    <p>They facilitate handling text instead of bytes</p> Signup and view all the answers

    Which method is NOT a key method of the java.io.OutputStream class?

    <p>read()</p> Signup and view all the answers

    What is the purpose of filter streams in Java I/O?

    <p>To convert raw bytes into other formats</p> Signup and view all the answers

    What should you do before closing an output stream to avoid data loss?

    <p>Flush the stream</p> Signup and view all the answers

    What is the primary function of BufferedOutputStream?

    <p>To temporarily store data until it is written to the output stream.</p> Signup and view all the answers

    Which of the following methods does an InputStream use?

    <p>read()</p> Signup and view all the answers

    Which type of stream is responsible for handling text in formats like UTF-8?

    <p>Readers/Writers</p> Signup and view all the answers

    What happens when you call the read() method of a BufferedInputStream with an empty buffer?

    <p>It reads directly from the source.</p> Signup and view all the answers

    Which predefined stream variables are included in the System class?

    <p>in, out, err</p> Signup and view all the answers

    What is the significance of autoFlush in PrintStream?

    <p>It flushes the stream after every print() or println() call.</p> Signup and view all the answers

    Which method is NOT part of OutputStream functionality?

    <p>print()</p> Signup and view all the answers

    What is the primary purpose of filter streams?

    <p>To manipulate raw data in bytes.</p> Signup and view all the answers

    What does the method isFile() return?

    <p>True if the object is a file.</p> Signup and view all the answers

    What is the function of the length() method?

    <p>Returns the file size in bytes.</p> Signup and view all the answers

    Which interface must a class implement to allow serialization?

    <p>Serializable</p> Signup and view all the answers

    What is the primary purpose of the ObjectOutputStream class?

    <p>To save entire objects to a file.</p> Signup and view all the answers

    What is the logical connection identified by a number called?

    <p>Port</p> Signup and view all the answers

    Which range of ports is reserved for 'well-known' services?

    <p>1-1023</p> Signup and view all the answers

    When a client connects to a server, what does it normally create to establish communication?

    <p>A socket</p> Signup and view all the answers

    What happens when the server receives a connection request from a client?

    <p>It creates a new socket for this specific client.</p> Signup and view all the answers

    What should you wrap around a FileReader to improve reading efficiency?

    <p>BufferedReader</p> Signup and view all the answers

    Which method is used to read a line from a BufferedReader?

    <p>readLine()</p> Signup and view all the answers

    What type of exception is thrown if a file cannot be found when using FileInputStream?

    <p>FileNotFoundException</p> Signup and view all the answers

    What will the canWrite() method return if the file is not writable?

    <p>false</p> Signup and view all the answers

    Which statement is true about the File methods?

    <p>exists() returns true if the file is present.</p> Signup and view all the answers

    What must be done after finishing file operations, such as using FileReader or FileWriter?

    <p>Close the file</p> Signup and view all the answers

    Which class handles byte streams for file operations in Java?

    <p>FileOutputStream</p> Signup and view all the answers

    What does the isDirectory() method indicate about the file object?

    <p>True if the object is a directory</p> Signup and view all the answers

    Study Notes

    Client-Server Architecture

    • Servers provide services to clients that connect to them.
    • A server operates on a hosting machine and responds when a client initiates communication.
    • Common server services include web page hosting.
    • Web browsers like Firefox and Chrome function as clients accessing web servers.

    Java I/O Streams

    • Java Input/Output is structured around streams, which are sequences of data.
    • Input streams read data, while output streams write data; both types share fundamental read and write methods.
    • Filter streams can modify data during the reading or writing process.
    • Readers and writers are specialized for text handling, converting it instead of just working with bytes.

    Output Streams

    • Java's output class is java.io.OutputStream, which includes key methods:
      • write(int b): Writes a single byte.
      • write(byte[] data): Writes an array of bytes.
      • write(byte[] data, int off, int len): Writes a portion of an array.
      • flush(): Ensures all buffered data is written out.
      • close(): Releases resources associated with the stream.

    Importance of Closing Streams

    • The close() method frees resources like file handles and network ports.
    • Closing the stream ends any associated network connection.
    • Attempting to write to a closed stream will throw an IOException.
    • Not closing streams in long-running applications can lead to resource leaks.

    Flushing Streams

    • Flushing a stream before closing prevents data loss.
    • It helps mitigate hard-to-diagnose errors that might arise from incomplete data writing.

    Input Streams

    • The core input class for Java is java.io.InputStream, with essential methods:
      • int read(): Reads a single byte.
      • int read(byte[] data): Reads bytes into an array.
      • int read(byte[] data, int off, int len): Reads bytes with an offset.
      • long skip(long n): Skips over a defined number of bytes.
      • int available(): Returns the number of bytes that can be read.
      • close(): Closes the stream and frees resources.
    • The end of a stream is signaled by returning -1.

    Filter Streams

    • Filter streams enhance byte streams by converting raw data formats, such as compression.
    • Two types of filters exist: filter streams (for bytes) and readers/writers (for text).
    • Both filter input and output streams support similar methods as their respective streams.

    Buffered Streams

    • BufferedOutputStream temporarily collects data in a buffer until it's full or flushed for efficiency.
    • Constructors for BufferedOutputStream include:
      • BufferedOutputStream(OutputStream out)
      • BufferedOutputStream(OutputStream out, int bufferSize)
    • BufferedInputStream uses a buffer to read data first and only fetches from the source if needed.
    • PrintStream is widely used, with System.out being a common instance.
    • Additional constructors for PrintStream allow attachment to other output streams, including auto-flushing functionality.
    • Features print() and println() methods for outputting various data types.

    Predefined Streams

    • Three predefined stream variables in the System class:
      • System.out: Standard output to the console.
      • System.in: Standard input from the keyboard.
      • System.err: Outputs error messages to the console.
    • System.in is an InputStream, while System.out and System.err are PrintStream objects.

    Readers and Writers

    • java.io.Reader and java.io.Writer classes are designed for character read/write operations using Unicode.
    • FileReader and FileWriter are specific for file reading and writing.
    • Methods in the Writer class support various forms of writing characters and include flush() and close().

    Input/Output Stream Classes

    • InputStreamReader: Converts bytes from an input stream to characters using encoding.
    • BufferedReader: Improves reading efficiency by utilizing a buffer.
    • File creation for reading and writing involves FileReader and FileWriter, typically wrapped around buffered or print streams for better performance.

    File Handling

    • Use FileInputStream and FileOutputStream for file operations.
    • Constructors throw FileNotFoundException if issues arise with file accessibility or existence.
    • File class methods (e.g., canRead(), delete(), exists(), length()) enable various file-related operations.

    Command-Line Parameters

    • Java allows passing parameters during execution, accessible in the main method via an array of Strings.

    Serialization

    • Serialization saves an object's state in a byte stream for persistent storage, retrievable through deserialization.
    • Classes implementing the Serializable interface can be serialized and deserialized using ObjectOutputStream and ObjectInputStream.

    Ports and Sockets

    • A port is a numbered connection point for services, ranging from 1 to 65,535, with ports 1-1023 being "well-known" for standard services.
    • Sockets facilitate communication between client and server, with each end of the connection represented by a socket.
    • Servers generate a dedicated socket for communication after receiving connection requests from clients.

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    Description

    This quiz explores the fundamentals of the client-server model and the concept of streams in Java I/O. You will learn about how servers provide services to clients and the basics of input and output streams in Java. Test your knowledge on web communication and stream operations!

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