4003-707-02 Advanced Programming
Module 6. I/O -- Lecture Notes

Byte-Level Input/Output

• Class java.io.File -- Represents a file

• Byte-level output
  • Write a sequence of bytes (numbers in the range 0..255)
  • Class java.io.OutputStream -- Base class for writing bytes
  • Class java.io.FileOutputStream -- Subclass for writing bytes to a file

• Byte-level input
  • Read a sequence of bytes (numbers in the range 0..255)
  • Class java.io.InputStream -- Base class for reading bytes
  • Class java.io.FileInputStream -- Subclass for reading bytes from a file

Character-Level Input/Output

• Convert a sequence of bytes to a sequence of characters (or vice versa) using a character encoding
  • ASCII
  • Unicode
  • UTF-8

• Character-level output
  • Write a sequence of characters
  • Class java.io.Writer -- Base class for writing characters
  • Class java.io.OutputStreamWriter -- Subclass for writing characters to an output stream

• Character-level input
  • Read a sequence of characters
  • Class java.io.Reader -- Base class for reading characters
  • Class java.io.InputStreamReader -- Subclass for reading characters from an input stream

High-Level Textual Input/Output

• Textual output
  • Print numbers of various types as human-readable character sequences
  • Class java.io.PrintStream -- prints using default character encoding
  • Class java.io.PrintWriter -- prints using a given character encoding
  • System.out -- A PrintStream for printing on the console ("standard output")
  • System.err -- A PrintStream for printing on the console ("standard error")
  • Creating A PrintStream that prints into a file

• Textual input
  • Parse numbers, words, lines, etc. from human-readable character sequences
  • Class java.util.Scanner
  • System.in -- An InputStream for reading from the console

Binary Data Input/Output

• Read and write values of primitive data types in the exact binary format in which the values are stored inside the CPU
  • int -- 4 bytes
  • double -- 8 bytes
  • See class java.io.DataOutputStream for others

• Binary data output
  • Class java.io.DataOutputStream

• Binary data input
  • Class java.io.DataInputStream

• Number of bytes written by PrintStream vs. number of bytes written by DataOutputStream

• Speeding up I/O for large files
  • Class java.io.BufferedOutputStream
  • Class java.io.BufferedInputStream

Object Input/Output

• Read and write entire objects as sequences of bytes
  • Serialization -- Convert an object to a sequence of bytes
  • Deserialization -- Convert a sequence of bytes back to an object

• Object output
  • Class java.io.ObjectOutputStream
  • The writeObject() method
  • Serializes the object and writes the sequence of bytes to the underlying output stream

• Object input
  • Class java.io.ObjectInputStream
  • The readObject() method
  • Reads the sequence of bytes from the underlying input stream and deserializes the object

• To be written by writeObject() or read by readObject():
  • The object's class must implement interface java.io.Serializable
  • The object's fields must be primitive types or serializable objects

Advanced Programming • 4003-707-02 • Fall Quarter 2008

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Alan Kaminsky • Department of Computer Science • Rochester Institute of Technology • 4486 + 2220 = 6706

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Copyright © 2008 Alan Kaminsky. All rights reserved. Last updated 16-Oct-2008. Please send comments to ark­@­cs.rit.edu.