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What are the two main types of streams described?

  • Input streams and Output streams
  • Byte streams and Character streams (correct)
  • File streams and Memory streams
  • Data streams and Character streams

    • What does the term 'streams' refer to in programming?

  • A sequence of data read from a source or written to a destination (correct)
  • A collection of files
  • A type of data storage
  • Connections between databases

    • Which abstract classes are provided for byte streams?

  • FileInputStream and FileOutputStream
  • DataStream and FileStream
  • InputStream and OutputStream (correct)
  • ByteStream and CharacterStream

    • Which of the following is NOT a source that a stream can be connected to?

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

    What type of data do character streams manipulate?

    <p>Text data (D)</p> Signup and view all the answers

    What is the primary focus when using streams in I/O operations?

    <p>Performing I/O operations on the stream (D)</p> Signup and view all the answers

    Which stream type manipulates data as bytes?

    <p>Byte streams (D)</p> Signup and view all the answers

    What does a stream abstract away from the user?

    <p>The connection to the data source (B)</p> Signup and view all the answers

    Which of the following is true about data stored in streams?

    <p>It has a higher-level structure beyond just bytes. (D)</p> Signup and view all the answers

    Which class in Java allows for both input and output operations to arbitrary data streams?

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

    Which method would you use to read a specified number of bytes from an input stream to an array starting from a defined offset?

    <p>int read(byte[] b, int offset, int length) (A)</p> Signup and view all the answers

    What is the primary function of the flush() method in output streams?

    <p>To write buffered data to the output device (C)</p> Signup and view all the answers

    Which class is specifically designed to improve I/O performance by using a buffer?

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

    What does the method exists() in the File class return?

    <p>True if the file or directory exists. (C)</p> Signup and view all the answers

    When writing to a text file, which class provides methods to output formatted text in lines?

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

    Which method would you use to write a single integer byte to an output stream?

    <p>int write(int c) (A)</p> Signup and view all the answers

    What is the main purpose of the BufferedInputStream class?

    <p>To improve reading performance by buffering. (B)</p> Signup and view all the answers

    Which method from the File class would rename an existing file?

    <p>boolean renameTo(File newName) (A)</p> Signup and view all the answers

    How does the readLines method read data from a file?

    <p>It reads line by line using BufferedReader. (D)</p> Signup and view all the answers

    Which class would you use to read primitive data types such as int or float from a file?

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

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    Flashcards

    Data Streams

    A sequence of data that is read from a source or written to a destination. Sources can be files, memory, keyboards, etc., while destinations can be files, memory, or screens.

    Byte Streams

    Manipulate data in bytes. Two abstract classes: InputStream and OutputStream.

    Character Streams

    Manipulate data as Unicode text streams.

    What is a stream connected to?

    Streams can be connected to a variety of sources and destinations, including files on floppy disks, hard disks, network connections, or even memory.

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    Why use streams?

    Streams abstract away the specifics of the source or destination, allowing us to focus on performing I/O operations on the data.

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    InputStream Class

    An abstract class used for reading data from a byte source.

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    OutputStream Class

    An abstract class used for writing data to a byte destination.

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    Data Storage

    Data is stored as a sequence of bytes, but can be interpreted as higher-level structures like characters or objects.

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    File I/O

    Streams are used to interact with files, allowing us to read data from files and write data to files.

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    Abstraction

    Streams abstract away the specifics of the source or destination, enabling us to work with data in a more generic way regardless of the underlying implementation.

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    InputStream

    A class that allows data to be read from a source, such as a file or network connection.

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    OutputStream

    A class that allows data to be written to a destination, such as a file or network connection.

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    BufferedReader

    A subclass of Reader that reads characters from a stream, but also provides buffering to improve performance. It can read data in blocks, making I/O operations faster.

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    BufferedWriter

    A subclass of Writer that writes characters to a stream, but also provides buffering to improve performance. It writes data in blocks, making I/O operations faster.

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    FileInputStream

    A class that allows reading data from a file.

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    FileOutputStream

    A class that allows writing data to a file.

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    File

    A class in Java that represents files and directories. It provides methods for creating, opening, querying information about files and directories.

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    FileReader

    A class that allows reading characters from a text file.

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    FileWriter

    A class that allows writing characters to a text file.

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    PrintWriter

    A class that allows writing data to a text file in a more efficient way, providing methods for writing data in lines rather than individual characters.

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    Study Notes

    Object-Oriented Programming: Streams and Files

    • Data Streams: Data is stored as a sequence of bytes. Higher-level structures like characters or objects can be considered sequences of bytes.
    • Streams: A sequence of data read from or written to a destination.
      • Source: Memory, keyboard, file.
      • Destination: Memory, screen, file.
    • Java programs use objects of different stream types to send and receive data.
    • Streams can be connected to various sources (floppy, hard disk, network, memory). The implementation abstracts away specific connections, focusing only on performing input/output (I/O) operations.
    • Types of Streams:
      • Byte streams: Manipulate data in bytes.
        • InputStream: Abstract base class for reading byte streams.
        • OutputStream: Abstract base class for writing byte streams.
      • Character streams: Manipulate data as Unicode text.
        • Reader: Abstract base class for reading character streams.
        • Writer: Abstract base class for writing character streams.

    Stream Hierarchies

    • InputStream Hierarchy: Shows subclasses of InputStream, like FileInputStream, PipedInputStream, DataInputStream, etc.
    • OutputStream Hierarchy: Shows subclasses of OutputStream, like FileOutputStream, PipedOutputStream, DataOutputStream, etc.
    • Reader Hierarchy: Shows subclasses of Reader, like BufferedReader, FileReader, InputStreamReader, etc.
    • Writer Hierarchy: Shows subclasses of Writer, like BufferedWriter, FileWriter, OutputStreamWriter, etc.

    Methods of InputStream

    • int read(): Reads the next byte of data from the input stream.
    • int read(byte[] b): Reads b.length bytes from the input stream to the byte array b.
    • int read(byte[] b, int offset, int length): Reads length bytes from the input stream to the byte array b starting at offset.
    • void close(): Closes the input stream.

    Methods of OutputStream

    • int write(int c): Writes the single byte c to the output stream.
    • int write(byte[] b): Writes b.length bytes from the byte array b to the output stream.
    • int write(byte[] b, int offset, int length): Writes length bytes from the byte array b, starting from offset, to the output stream.
    • void close(): Closes the output stream.
    • void flush(): Flushes the data from the buffer to the output stream.

    Methods of Reader

    • int read(): Reads the next character from the input stream.
    • int read(char[] cbuf): Reads cbuf.length characters from the input stream to the char array cbuf.
    • int read(char[] cbuf, int off, int len): Reads len characters from the input stream to the char array cbuf, starting at offset off.
    • void close(): Closes the input stream.

    Methods of Writer

    • int write(int c): Writes the single character c to the output stream.
    • int write(char[] cbuf): Writes cbuf.length characters from the char array cbuf to the output stream.
    • int write(char[] cbuf, int off, int len): Writes len characters from the char array cbuf, starting at offset off, to the stream.
    • void close(): Closes the output stream.
    • void flush(): Flushes the data stream from the buffer to the output stream.

    Important Stream Types

    • InputStream/OutputStream: Base classes with few features.
    • FileInputStream/FileOutputStream: Specifically for connecting to files.
    • BufferedInputStream/BufferedOutputStream: Improve I/O performance by adding buffers.
    • BufferedReader/BufferedWriter: Convert bytes to Unicode characters and strings.

    Input/Output Stream Object

    • To read/write data, a stream object is needed.
    • The I/O stream object is attached to a data source or destination.
    • Example: BufferedReader in = new BufferedReader(new FileReader(filename));

    Use of Buffered Streams

    • Buffering improves I/O performance by reading/writing data in blocks.
    • Reduces the number of accesses to I/O devices.
    • Data is written to a buffer, and when it fills, it's transferred to the destination.
    • The flush() method forces data to be written to destination.
    • Data is read from the buffer when it's not empty.

    Standard I/O Streams

    • Java.lang package includes System.out and System.err (PrintStream).
      • These can be used directly to print to the standard output and error streams.
    • System.in is an InputStream object, used with InputStreamReader and BufferedReader.

    The File Class

    • In java.io package, provides basic file and directory operations.
    • Files are not streams; they represent a file structure.
    • Create/open files.
    • Query directory information.

    Create a File Object

    • File myFile = new File("data.txt"); or File myFile = new File("myDocs", "data.txt");
    • Directories are treated the same as files. Example: File myDir = new File("myDocs");

    File's Methods

    • File/directory name: getName(), getPath(), getAbsolutePath(), getParent(), renameTo(File newName)
    • File/directory status: exists(), canWrite(), canRead(), isFile(), isDirectory()
    • Status: lastModified(), length(), delete()
    • Directory: mkdir(), list()

    Manipulate Text Files

    • Read: FileReader (for individual characters), BufferedReader(for reading lines).
    • Write: FileWriter (for individual characters), PrintWriter (for writing lines).

    Read from a Text File

    • Uses a BufferedReader, typically linked to a FileReader, to read lines from a file until the end of the file.
    • The readLine() method is used to read lines from the file, and the returned string is printed to the console.

    Write to a Text File

    • Uses a PrintWriter, typically linked to FileWriter, to write lines into the file.
    • out.write() is used to write formatted data or strings into the file.

    Manipulate Binary Files

    • Read: FileInputStream, DataInputStream, ObjectInputStream
    • Write: FileOutputStream, DataOutputStream, ObjectOutputStream

    DataInputStream/DataOutputStream

    • DataInputStream: Reads primitive data types. -Methods include readBoolean, readByte, readChar, readShort, readInt, readLong, readFloat, readDouble.
    • DataOutputStream: Writes primitive data types.
      • Methods include writeBoolean, writeByte, writeChar, writeShort, writeInt, writeLong, writeFloat, writeDouble

    Write Primitive Data

    • Code example showing how to write primitive data to a binary file using FileOutputStream and DataOutputStream.

    Read Primitive Data

    • Code example showing how to read primitive data from a binary file using FileInputStream and DataInputStream.

    File of Objects

    • Objects can be stored in files by using serialization.
    • Data classes must implement the Serializable interface to be serialized.

    Write Object

    • The code to write an object to a file, using serialization with ObjectOutputStream and FileOutputStream.

    Read Objects

    • The code to read an object from a file using deserialization with ObjectInputStream and FileInputStream.

    RandomAccessFile Class

    • Implements DataInput and DataOutput interfaces.
    • Enables random access to data within a file.
    • Allows reading and writing data at specific byte offsets.

    Write with RandomAccessFile

    • Code example for writing to a file using RandomAccessFile.

    Read with RandomAccessFile

    • Code example for reading from a file using RandomAccessFile.

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