Overview of Java programming projects for 3345 Programming

							    Overview of Java
programming projects for
          3345
 Programming assignments: submission

•.java files via WebCT, you may put them in one folder and archive
them together

•readme.txt with instructions how to compile and run your code,
format of the input, your assumptions, known bugs and limitations
etc. Do not write: program is self-explanatory, contact me with
questions you may have.

•sample input and output files, if any

•makefile (optional)

•presentation of an assignment may be required, short questions may
be asked
 Programming assignments:
 development and coding
 Submit neat well-indented code, part of the grade is for code


 Provide enough comments (each variable (except loop iterators),
   function, block of code)

 For your own benefit, you may want to learn of javadoc or doxygen


 Follow good naming conventions


 Code optimization vs. development time and readability: the
   example below is hard to read

for(;P("\n"),R-;P("|"))
for(e=C;e-;P("_"+(*u++/8)%2))P("|"+(*u/4)%2);
  Programming assignments:
  development and coding
 Simple and working program is better than sophisticated and not
   working one. Bells and whistles go unnoticed when the basic
   functionality is poor.

 Develop with re-using in mind: some of the routines of the first project
   (input\output, GUI) may be reused in the second project

 Always make backups and always keep a running copy of your code!


 If stuck in debugging, localize (isolate) errors: comment all your code,
   insert only the “Hello, world!” line. See whether the program runs,
   gradually adding pieces of your code.
Programming assignments: run time issues

  Catch exceptions, exit gracefully, acknowledge exiting.


  One should be able to easily understand how to interact with the
    program, i.e. give meaningful labels to input fields, prompt for
    input in command-line interface.

  Program should be easy to use


  Don‟t hard-code the input data, yet you may use randomly
    generated numbers as the input
      Programming assignments
   It was agreed in class that the following environments are used to develop
   the projects:
      NetBeans
      JBuilder
      JCreator
      Eclipse
      or text editor


Please, stick to these options. Download the latest version of your favorite
   environment before you start.
Using Unix machines

 Putty tool to connect to
        apache.utdallas.edu, ssh net01

 New rules: net01-net50 machines cannot be used in this class


 javac to compile programs, java to run programs


 Makefiles and tarballs
  Honor code
 OK to use provided code examples

 No code from the book or web. If you need to use external code for
   some additional features, clearly specify the parts of the code that
   are not yours.

 Projects are individual. Explicitly acknowledge any cooperation.

 Using the standard Tree and Graph libraries is not allowed. Write
   your own classes corresponding to the objects.
Java code concepts

 Source code written to .java
 Compiled using javac to .class
 A .class file does not contain code that is native to a given
   processor; it instead contains bytecodes-- the machine
   language of the Java Virtual Machine. The Java launcher tool
   (java) then runs the application with an instance of the Java
   Virtual Machine.
 Platform: hardware or software environment in which a program
  runs.
 Java platform: software only
 2 components
        The Java Virtual Machine
        The Java Application Programming Interface (API)
Java platform
 One should have
     Java Runtime Engine (JRE) to run java
      applications
     Java Source Development Kit (SDK/JDK) to
      compile .java into .class
     Optionally, the development environment.
 Popular example

package javalecture;

 public class FirstClass {

      public static void main(String[] args) {

      System.out.println("I think therefore I
    think I am!");
      }

}

Try to explain the underlined terms before looking at the next
  slide.
Package: a unique namespace for the types it contains; classes in the
  same package can access each other's protected members.


Public: class is visible to all classes everywhere.
No modifier: visible only within its own package.

Member (function) level:
  Public, no modifier: same meaning
  Private: can only be accessed in its own class
  Protected: can only be accessed within its own package and, in
  addition, by a subclass of its class in another package.

Instance methods are associated with an object and use the instance
   variables of that object. This is the default.
Static methods take all they data from parameters and compute
   something from those parameters, with no reference to variables.
   This is typical of methods which do some kind of generic calculation.
            Abstract classes and interfaces
An abstract class is a class that is declared abstract and may include abstract
methods (methods not implemented). Abstract classes cannot be instantiated,
but they can be subclassed. In Java, EVERY class is a subclass of
java.lang.Object (or subclass of its subclasses).

abstract class Account {
int amount;
void withdraw(double number) { ... }
abstract void changeBalance(); }

An interface: an abstract class declared as interface
 all variables are static and final
 only method signatures included, no method implementations.

Interface PrintableObject{
  static final Integer MaximumSizeInBytes=256;
  void print(); }
 Extends vs implements

final class InterestBearingAccount extends Account:
Class InterestBearingAccount (subclass) inherits all members
   (variables and functions) of class Account (superclass).

class Image implements PrintableObject:
Class Image provides implementation to methods of the class
   PrintableObject (e.g. method print() that would specify how exactly
   to print images).

Interfaces are used to encode similarities which classes of various
   types share, but do not necessarily constitute a class relationship
   (e.g. Image and Text classes).

A class which implements an interface must either implement all
   methods in the interface, or be an abstract class.
             Popular example using Swing
package javalecture;

import javax.swing.JFrame;
import javax.swing.JLabel;

public class HelloWorld {
    public static void main(String[] args) {

         JFrame Frame = new JFrame ("Hello, World!");

         Frame.setDefaultCloseOperation
    (JFrame.DISPOSE_ON_CLOSE);

         Frame.getContentPane().add (new JLabel("Hello,
    World!"));

         Frame.pack();

         Frame.setVisible(true);
     }
}
import java.awt.*;
                   Draw with Swing
import javax.swing.*;

public class Drawing {
    public static void main(String[] args) {
            new Drawing();
        }

    Drawing() {
    JFrame frame = new JFrame();
      frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);

    frame.getContentPane().add(new MyComponent());

             frame.repaint();

             frame.setSize(300, 300);
             frame.setVisible(true);
         }
}
               Draw with Swing
class MyComponent extends JComponent {

        public void paintComponent(Graphics g) {
           super.paintComponent(g);

                // Draw an oval that fills the window
                int x = 0;
                int y = 0;
                int width = getSize().width-1;
                int height = getSize().height-1;

                g.drawOval(x, y, width, height);

           }
       }
          Create conten pane

public JPanel createContentPane (){

        //Create and set up the content pane.
       ContentPanel = new JPanel();
       ContentPanel.setLayout(null);

       SubmitButton = new JButton("Square!");
       SubmitButton.setLocation(5, 220);
       SubmitButton.setSize(100, 30);
       SubmitButton.addActionListener(this);
       ContentPanel.add(SubmitButton);
    Create conten pane
ClearButton = new JButton("Clear...");
        ClearButton.setLocation(5, 280);
        ClearButton.setSize(100, 30);

ClearButton.addActionListener(this);
        ContentPanel.add(ClearButton);

       // Insert Textfields
       XField = new JTextField(3);
       XField.setLocation(5, 30);
       XField.setSize(100, 30);
       ContentPanel.add(XField);

       ContentPanel.setOpaque(true);

       return ContentPanel;
       }
          Process button click
public void actionPerformed(ActionEvent e) {
        if(e.getSource()==SubmitButton){
            //get the data from the text fields
            Integer x;
            x=
  Integer.parseInt(XField.getText().trim());

           Integer z;
           z=x*x;
           XField.setText(z.toString());
          }
        else if(e.getSource()==ClearButton){
           //clean the fields
           XField.setText("");}
   }
              Create and show GUI
private static void createAndShowGUI() {

        //This is to turn on the Default 'Look and Feel'.
        JFrame.setDefaultLookAndFeelDecorated(true);

        Frame = new JFrame ("Multiplicator!");

        ButtonEx demo = new ButtonEx();
        Frame.setContentPane(demo.createContentPane());


  Frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);

        Frame.setSize(800,600);
        Frame.setVisible(true);

    }
         Combine all
import java.util.*;
import javax.swing.*;

import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;

public class ButtonEx implements ActionListener{

   static JTextField XField;
   JButton SubmitButton, ClearButton ;
   JPanel ContentPanel;
   static JFrame Frame;
   public static void main(String[] args) {
               createAndShowGUI();
 }}
public int readFromFile(){
     try{
                                Read from file
      fin = new FileInputStream ("input.txt");
       BufferedReader reading = new BufferedReader(new
  InputStreamReader(fin));

       String thisLine;

       //while not the end of file
       while ((thisLine = reading.readLine()) != null) {
           counter++; }

      //close the input file
      fin.close(); }
    catch (IOException e)
       { System.err.println ("Unable to read from file");
           return -1; }

   finally{
         System.out.println("file reading completed");
         return counter; } }
Stream tokenizer
One option to read file with entries delimited by
a custom symbol (set of symbols) is to read line
by line and use an object of class
StringTokenizer to extract each entry.


For details, check:
  http://java.sun.com/j2se/1.4.2/docs/api/java/util/StringTokenizer.html
                          Write to file
public void writeToFile(int n){

        try {
            BufferedWriter writting=new
  BufferedWriter(new FileWriter("output.txt"));
            writting.write("Total number of strings in
  input file: " + n );

            writting.close();
            }
        catch (IOException e)
            {
            System.err.println ("Unable to write to
  file");
            }
        finally{
            System.out.println("This is a last action");
        }

   }
Exercises
 For using in the projects: draw an oval on a
  button click
 For your own interest: make your java
  application look like „usual‟ OS application.
  Set your own icon for the application. Make
  application window appear in the center of
  the screen.
 These are optional, no grades involved.