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Intro to Java

Intro to Java. Java Applications Swing Class Graphics. Java Outline. Today Intro and Applications GUI Client / Server RMI, JDBC. JAVA Implementation. Java program. Java program. Java program. Java program. Java Cmds. Java Cmds. Java Cmds. VM. VM. VM. SPARC. PowerPC. Intel.

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Intro to Java

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  1. Intro to Java Java Applications Swing Class Graphics

  2. Java Outline • Today • Intro and Applications • GUI • Client / Server • RMI, JDBC

  3. JAVA Implementation Java program Java program Java program Java program Java Cmds Java Cmds Java Cmds VM VM VM SPARC PowerPC Intel

  4. Operations Environments • Applications program (~DOS window) • supports file access • Applet (browser) – no longer generally supported • supports Internet linkages.

  5. Building Java Applications Using Java Development Kit • Get a copy of the JDK (www.oracle.com, etc.) • Install the development kit (tools and classes) • Create MyApp.java source file • text editor (notepad, etc.) • winedit, Café, etc. • Compile .java file to create .class file • javac MyApp.java • Run application (.class file) through java VM • java MyApp

  6. Building Java Applications Using Java IDEs • NetBeans • Available from netbeans.org • Eclipse • Available from www.eclipse.org • jCreator le • available from jcreator.com • jcreator pro – academic license $35 • jDeveloper • available from www.oracle.com/technetwork/developer-tools/jdev • many others

  7. Sample Java App G:\Data\Java\MyHelloApp>type MyHelloApp.java class MyHelloApp { public static void main (String argv[]) { String message[] = new String[2]; message[0] = "Welcome to CS423"; message[1] = "The subject is JAVA!"; System.out.println (message[0]); System.out.println (message[1]); } }

  8. MyHelloApp Implementation MyHelloApp.java Java compiler MyHelloApp.class MyHelloApp.class Java byte code VM machine code

  9. Sample Java App G:\Data\Java\MyHelloApp>javac MyHelloApp.java G:\Data\Java\MyHelloApp>java MyHelloApp Welcome to CS423 The subject is JAVA! G:\Data\Java\MyHelloApp>

  10. MyHelloApp.class

  11. Get Input from User import java.io.*; class InputApp { InputApp () { DataInputStream dis = new DataInputStream (System.in); String sIn = " "; String sOut = " "; File fIn; File fOut; FileInputStream fis; FileOutputStream fos; int iNumBytesRead; byte[] ab;

  12. Get Input from User System.out.println ("*-------------------------------------------*"); System.out.print ("Enter Source File Name Here: "); System.out.flush (); try {sIn = dis.readLine ();} catch (Exception e) {System.out.println ("Exception on input file name" + e);} System.out.print("Enter Destination File Name Here: "); System.out.flush (); try {sOut = dis.readLine ();} catch (Exception e) {System.out.println ("Exception on output file name" + e);}

  13. Get Input from User try { fIn = new File (sIn); fis = new FileInputStream (fIn); fOut = new File (sOut); fos = new FileOutputStream (fOut); ab = new byte[2048]; while ((iNumBytesRead = fis.read (ab)) != -1) { fos.write (ab, 0, iNumBytesRead); } fis.close (); fos.close (); } catch (Exception e) {System.out.println ("Exception during copy: " + e); }

  14. Get Input from User System.out.println ("Data copied from " + sIn + " to " + sOut); System.out.println ("*-------------------------------------------*"); } public static void main (String args[]) { new InputApp (); } }

  15. Get Input from User G:\Data\Java\InputApp>java InputApp *-------------------------------------------* Enter Source File Name Here: books_db.txt Enter Destination File Name Here: My_list.txt Data copied from books_db.txt to My_list.txt *-------------------------------------------* G:\Data\Java\InputApp>

  16. Swing Components • Defined in package javax.swing • Pure Java components • AWT components tied to local platform GUI • UNIX java windows look like X windows • Windows java windows look like Windows windows (??) • etc. • Swing defines a common look and feel for Java.

  17. Product.java // From Java: How to Program - Deitel and Deitel // Calculate the product of three integers import javax.swing.JOptionPane; public class Product { public static void main( String args[] ) { int x, y, z, result; String xVal, yVal, zVal; xVal = JOptionPane.showInputDialog( "Enter first integer:" ); yVal = JOptionPane.showInputDialog( "Enter second integer:" ); zVal = JOptionPane.showInputDialog( "Enter third integer:" );

  18. Product.java x = Integer.parseInt( xVal ); y = Integer.parseInt( yVal ); z = Integer.parseInt( zVal ); result = x * y * z; JOptionPane.showMessageDialog( null, "The product is " + result ); System.exit( 0 ); } }

  19. Product Output(s)

  20. JOptionPane • Similar to windows message boxes • Types of Option Panes: showConfirmDialog(null,message,title,optionType,msgType); Asks a confirming question, like yes/no/cancel. showInputDialog(message); Prompt for some input. showMessageDialog(null, message); Tell the user about something that has happened. showOptionDialog(....); The Grand Unification of the above three.

  21. Additional Swing Options JOptionPane.showMessageDialog(null, "This is an alert", "Alert", JOptionPane.ERROR_MESSAGE); JOptionPane.showConfirmDialog(null, "Is that your final answer?", "Choice Dialog", JOptionPane.YES_NO_OPTION);

  22. Additional Swing Options Object[] options = { "Lady", "Tiger" }; choice = JOptionPane.showOptionDialog(null, "What will it be -\nThe Lady or the Tiger?", "Decision", JOptionPane.DEFAULT_OPTION, JOptionPane.QUESTION_MESSAGE, null, options, options[0]); if (choice == 0) JOptionPane.showMessageDialog( null, "You chose the Lady", "Result", JOptionPane.PLAIN_MESSAGE ); else JOptionPane.showMessageDialog( null, "You chose the Tiger", "Result", JOptionPane.PLAIN_MESSAGE );

  23. Additional Swing Options Object[] possibleValues = { "First", "Second", "Third" }; Object selectedValue = JOptionPane.showInputDialog(null, "Choose one", "Input", JOptionPane.INFORMATION_MESSAGE, null, possibleValues, possibleValues[0]);

  24. Graphics in Applications • Must include a main() method • Must extend the AWT Frame class, or swing JFrame class

  25. HelloWorldWindow import java.awt.*; import java.awt.event.*; public class HelloWorldWindow implements WindowListener { public HelloWorldWindow() { myFrame f=new myFrame(); f.addWindowListener (this); } public void windowClosing(WindowEvent e) { System.out.println ("Closing Window"); System.exit(0); }

  26. HelloWorldWindow class myFrame extends Frame{ myFrame() { this.setSize(300, 200); this.show(); } public void paint(Graphics g) { String str = "A Windows version of Hello, World"; g.drawString(str, 25, 75); } public static void main(String[] args) { Frame f = new HelloWorldWindow(); f.resize(300, 200); f.show(); } } }

  27. HelloWorldWindow Output

  28. public void paint (Graphics g) • Provides an initial presentation of Graphics • Works on Graphics object • (like device context). • Place to store settings for screen output (text, images. etc.) • Must be regenerated following changes.

  29. Event Driven Programming • Operating System recognizes an event • Sends a signal to appropriate object • Object receives event notification and calls appropriate function public void windowClosing(WindowEvent e) { System.out.println ("Closing Window"); System.exit(0); }

  30. Object Layout • BorderLayout (default for Frames) • FlowLayout (default for Panels) • GridLayout • GridbagLayout • CardLayout • Fixed: • object.reshape (x, y, width, height);

  31. nuTextTest Example Linux Windows

  32. NuTextTest2.java import javax.swing.*; import java.awt.*; import java.awt.event.*; public class NuTextTest2 extends JFrame { public NuTextTest2() { setTitle("NuTextTest2"); Container p = getContentPane();; p.setLayout(new FlowLayout()); TickButton = new Button("Tick"); p.add(TickButton); TickButton.addActionListener( new ActionListener() { public void actionPerformed (ActionEvent e) { int minutes = Integer.parseInt(minuteField.getText()); minutes += 1; String min = String.valueOf(minutes); minuteField.setText(min); } } //end of ActionListener ); //end of TickButton

  33. NuTextTest2.java SetTime = new Button("Set Time"); p.add(SetTime); SetTime.addActionListener( new ActionListener() { public void actionPerformed (ActionEvent e) { String tim = hourField.getText()+ ":" + minuteField.getText(); timeField.setText(tim); } } );

  34. NuTextTest2.java hourField = new TextField("12", 3); p.add(hourField); minuteField = new TextField("00", 3); p.add(minuteField); timeField = new TextField("", 12); p.add(timeField); setSize (400,100); show (); }//end of NuTextTest2 (constructor) private TextField hourField; private TextField minuteField; private TextField timeField; private Button TickButton; private Button SetTime;

  35. NuTextTest2.java public static void main(String[] args) { NuTextTest2 app = new NuTextTest2(); app.addWindowListener( new WindowAdapter() { public void windowClosing( WindowEvent e ) { System.exit( 0 ); } } ); }//end of main() }//end of program

  36. Summary • Java is: • Platform independent • Object-oriented • Dynamic • Flexible – used in many different domains • Command line or graphical

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