Simple I/O

We are going to use two simple, but useful classes that help us do I/O:

• BasicDataWriter
• BasicDataReader

Note - not part of Java per se. Were defined and developed by Prof. Turner as part of the Clemson University Computer Science Java class library.

• Shows you can extend a programming language with your own classes. Cool!
• In this case, extend Java with some simple I/O facilities
• We'll create more later.
• Why not stick with System.out.println, etc.? We could, in fact. But we want to do more fancy things, etc., this will be better (we hope)
• CUCS = Clemson University Computer Science (in case you are wondering)

The class: BasicDataWriter

• Defines methods: (perhaps show online doc later)
  • BasicDataWriter () - constructor with no args, creates an output stream to monitor
  • BasicDataWriter (String fileName) - constructor with a single arg, i.e., name of file to write to - Notes:
    1. notation String fileName - argument of type of String, where fileName is a placeholder
    2. will create new file if does not already exist
    3. will replace existing file
    4. privs...yugh
  • write (String arg) - writes given string to output stream ( recall System.out.print)
  • writeln (String arg) - writes given string to output stream with a new line (recall System.out.println)
  • close () - closes the output stream - a good idea - tidy!
• So, can use two different constructors to create either output to monitor or output to a file
• Seems very basic. Are there other methods? Yes..
• Can we have more than one BasicDataWriter open at once? Sure. How?
• Can save to a file and later look at with editor
• Or can read file from a program. Hey an editor is a program. How can we do that?

The class: BasicDataReader

• Defines methods: (perhaps show online doc later)
  • BasicDataReader () - constructor with no args, creates an input stream to monitor
  • BasicDataReader (String fileName) - constructor with a single arg, i.e., name of file to read from - Notes:
    1. notation String fileName - argument of type of String, where fileName is a placeholder
    2. file must exist!
    3. privs...yugh
  • String readWord () - reads a single word (ignore whitespace)
  • String readLine () - reads an entire line
    • really contents of remaining current line, e.g., s = readWord; l = readLine();
  • close () - closes the output stream - a good idea - tidy!
• So, can use two different constructors to create either input to monitor or input from a file
• Seems very basic. Are there other methods? Yes..
• Can we have more than one BasicDataReader open at once? Sure. How?
• Can now write very general programs.

Example

import cucs.*;
class tryit {
  public static void main (String args[]) {
    BasicDataReader fromKeyboard = new BasicDataReader ();
    BasicDataWriter toMonitor = new BasicDataWriter ();
    BasicDataWriter toFile = new BasicDataWriter ("DATA.TXT");
    String s;

    toMonitor.write ("Enter your name> ");
    s = fromKeyboard.readLine ();
    toFile.writeln (s);
    toMonitor.write ("Enter your favorite book> ");
    s = fromKeyboard.readLine ();
    toFile.writeln (s);
  
    toFile.close ();
    toMonitor.close ();
    fromKeyboard.close ();

  }
}