File IO
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Questions and Answers

Which interface is implemented by classes whose objects represent a file or directory?

  • Path (correct)
  • directoryStream
  • Files
  • Paths

    • Which class has static methods that get a Path object that represents a file or directory location?

  • Paths (correct)
  • Files
  • directoryStream
  • Path

    • What is the purpose of the Files class?

  • To loop through directory contents
  • To manipulate files: create, copy and delete files (correct)
  • To get file and directory information
  • To convert CSV to Text files

    • What is the separator used in CSV files?

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

    How are values within a row separated in a CSV file?

    <p>By commas (,)</p> Signup and view all the answers

    What is the format of a CSV file?

    <p>Name, Age, City</p> Signup and view all the answers

    What is the purpose of the directoryStream interface?

    <p>To loop through directory contents</p> Signup and view all the answers

    What type of file uses semicolons (;) as separators?

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

    What is the difference between CSV and Text files?

    <p>CSV uses commas, Text uses semicolons</p> Signup and view all the answers

    What is the format of a Text file?

    <p>Name; Age; City</p> Signup and view all the answers

    What is a key difference between a variable and a file in terms of data storage?

    <p>Variables store temporary data, while files store permanent data.</p> Signup and view all the answers

    What is the purpose of the end-of-file marker in Java?

    <p>To mark the end of a file.</p> Signup and view all the answers

    What type of files are created by byte-based streams in Java?

    <p>Binary files</p> Signup and view all the answers

    What package is used to import file and directory information in Java?

    <p>java.nio</p> Signup and view all the answers

    What is the purpose of the Scanner class in Java?

    <p>To read input data.</p> Signup and view all the answers

    What is the difference between character-based streams and byte-based streams in Java?

    <p>Character-based streams create text files, while byte-based streams create binary files.</p> Signup and view all the answers

    What is the purpose of serialization in Java?

    <p>To read and write objects.</p> Signup and view all the answers

    How many bytes are used to represent each character in character-based streams in Java?

    <p>2 bytes</p> Signup and view all the answers

    What is the main difference between text files and binary files?

    <p>Text files store data in characters, while binary files store data in bytes.</p> Signup and view all the answers

    What is the purpose of the Formatter class in Java?

    <p>To format data for output.</p> Signup and view all the answers

    What is included in a serialized object?

    <p>The object's data and its type information</p> Signup and view all the answers

    What is the purpose of the ObjectOutputStream class?

    <p>To write objects to a stream</p> Signup and view all the answers

    What is necessary to use serialization with files?

    <p>Initialize both ObjectInputStream and ObjectOutputStream objects</p> Signup and view all the answers

    What is the main purpose of serialization?

    <p>To read and write objects to a file</p> Signup and view all the answers

    What is the relationship between ObjectInputStream and ObjectOutput?

    <p>They are two separate classes that implement ObjectInput and ObjectOutput interfaces</p> Signup and view all the answers

    What happens when an object is deserialized?

    <p>The object is recreated in memory</p> Signup and view all the answers

    What is the purpose of the ObjectInputStream class?

    <p>To read objects from a stream</p> Signup and view all the answers

    Why are ObjectOutputStream and ObjectInputStream necessary?

    <p>To read and write entire objects</p> Signup and view all the answers

    What is serialization used for?

    <p>To read and write entire objects</p> Signup and view all the answers

    What is the result of deserializing an object?

    <p>The object is recreated in memory</p> Signup and view all the answers

    What is the purpose of the Scanner class in Java?

    <p>To read information from a text file</p> Signup and view all the answers

    What is the consequence of not providing a path when using a Formatter?

    <p>The file will be created in the default directory</p> Signup and view all the answers

    What is the purpose of the Formatter class in Java?

    <p>To write formatted strings to a file</p> Signup and view all the answers

    What is the consequence of attempting to write to a file without permission?

    <p>A SecurityException will be thrown</p> Signup and view all the answers

    What is the purpose of System.exit?

    <p>To terminate an application</p> Signup and view all the answers

    What is the significance of an argument of 0 when using System.exit?

    <p>It indicates successful program termination</p> Signup and view all the answers

    What is the purpose of object serialization in Java?

    <p>To read or write an entire object to or from a file</p> Signup and view all the answers

    What exception is thrown when a file does not exist and cannot be created?

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

    What exception is thrown when the data being read by a Scanner method is in the wrong format?

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

    What exception is thrown when a Formatter is closed and an attempt is made to output to it?

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

    Study Notes

    File I/O

    • A computer file is a permanent storage of data, unlike variables and arrays which are temporary.
    • There are two basic types of computer files: Text files and Binary files.

    Files and Streams

    • Each file is viewed as a stream of bytes by Java.
    • There are two types of streams: Byte-based streams (input and output data in byte format, creates binary files) and Character-based streams (input and output data in character format, creates text files).

    NIO Classes and Interfaces

    • The java.nio package has classes and interfaces to get file and directory information: path, directoryStream, paths, files.
    • The Path interface is implemented by classes whose objects represent a file or directory.
    • The directoryStream interface is implemented by classes to loop through directory contents.
    • The Paths class has static methods that get a Path object that represents a file or directory location.
    • The Files class has static methods for manipulating files: create, copy, and delete files.

    CSV File vs Text File

    • CSV files use commas as separators, while text files use separators such as commas, colons, or semicolons.
    • CSV files have each subsequent line representing a data row, with values within a row separated by commas.

    Reading and Writing Files

    • The Scanner class is used to read text files.
    • The Formatter class is used to write formatted strings to a specified stream.

    Exceptions

    • SecurityException: occurs if the user does not have permission to write data to the file.
    • FileNotFoundException: occurs if the file does not exist and a new file cannot be created.
    • NoSuchElementException: if the data being read by a Scanner method is in the wrong format or if there is no more data to input.
    • FormatterClosedException: if the Formatter is closed when attempting to output.

    Object Serialization

    • Object Serialization is the process of converting an object into a byte stream, which can be written to a file.
    • The ObjectOutputStream and ObjectInputStream classes (in the java.io package) enable entire objects to be read from or written to a stream.
    • Serialization is used to read an entire object from or write an entire object to a file.

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    Related Documents

    10_Files IO and Serialization - 2.pdf

    Description

    This quiz covers the basics of object-oriented programming in Java, including file I/O operations. Designed for students in Computer Engineering Technology and Computer Science programs.

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