Streams

1
Streams

• Robert Stumpf, Professor
• Computer Information Systems
• California State Polytechnic University, Pomona

2
Input/Output

• Input
• Output
• Keyboard input
• Network input
• (Recall for security reasons there is no
  network output)

3
Input/Output

• Sun has created a large number of ways to handle
  streams of data from files
• Your instructor has chosen only one of ways to
  illustrate this
• They are
• BufferedReader and PrintWriter (streams)
• and
• FileReader and FileWriter (files)
• InputStreamReader (keyboard)

4
Input/Output

• Steams are a sequence of characters being piped
  through a method
• Files are a model of the physical files on the
  system
• Both files and streams are needed to make a file
  read work

5
Input

• Input example
• BufferedReader in
• in new BufferedReader (new FileReader
  ("file.txt"))

6
Input

• To read a record
• String line
• line in.readLine ( )
• To check if end of file
• line! null

7
Input

• Best to use loop
• line in.readLine ( )
• while (line ! null)
• System.out.println (line )
• line in.readLine ( )

8
Output

• Output example
• PrintWriter out
• outputFile new PrintWriter
• (new FileWriter (file.txt"))

9
Output

• To write a record with carriage return and line
  feed
• out.println (line)
• To write a record with out carriage return and
  line feed
• out.print (line)

10
Keyboard Input

• Just substitute System.in for input file name
• For example
• BufferedReader keyboard
• String line
• keyboard new BufferedReader
• (new InputStreamReader (System.in))
• System.out.println ("Enter a line ")
• line keyboard.readLine ( )

11
Network Input

• For example
• BufferedReader inputFile
• String inputLine
• try
• URL url new URL
  (getDocumentBase ( ) , file.txt)
• in new BufferedReader
  (url.openStream( ) )
• line in.readLine ( )

12
Network Input

• Note try statement the catches are
• catch (MalformedURLException exception)
  System.out.println (exception)
• catch (IOException exception)
• System.out.println (exception)
• catch (SecurityException exception)
• System.out.println (exception)

13
Summary

• Practice and test your work
• Leave the catches in as many problems surface
• Remember a stream is just characters in motion

14
Thank You

• Streams are very capable
• Any questions should be directed to Professor
  Robert Stumpf
• Email rvstumpf_at_csupomona.edu
• Web Sitehttp//www.csupomona.edu/rvstumpf