Java class Structure..

Tips for Beginners.....

This post is for the beginners.If you'v just started to learning java then try following tips and enjoy fast and easier java development........

1.Use sun's JavaSE JDK1.6 (available at: http://www.oracle.com/technetwork/java/javase/downloads/index.html)

2.Use Java6 documentation to explore java (available at: http://download.oracle.com/javase/6/docs/api/)

3.Use Netbeans6.9.1 IDE (available at: http://netbeans.org/downloads/index.html)

Now first  download these.Then follow following steps......

1.Install JavaSe6 and set the path for javac.

     To set path in windows first navigate to C:\Program Files\Java\jdk1.6.0_21\bin and find javac.exe and right click to javac and copy the path.Now go to desktop right click on My Computer then click Properties now click on advanced tab and the click on Environment Variable button the select path and edit then go to end of line and terminate with ";" and then paste the path now click Ok. To check the path write javac on cmd if no error found and list of commands appears means path is set successfully.

2.Install Netbeans and activate the java SE.To do so select new project from file and then select Java Project.

Now your java se in netbeans is activate.

Now to learn how to use netbeans IDE  use following tips.......

To do any think in Netbeans we have to make a project.

1.So start working with netbeans.File|New Project.Select Java in categories and and java application in projects.

2.Now then File|New File.Then select Java in categories and Java Class in file type and specify the name.

Now you can make your application here to run use Shift+f6.

For more info to use Netbeans IDE log on to http://netbeans.org/kb/docs/java/quickstart.html.

Creating Executable jar in Java

    Jar files are created using the jar.exe utility program from JDK.  You can make your jar file executable by defining the main class.  For thist, you  need to create a manifest file.  A manifest file is a one-line text file with a "Main-Class" directive.  For example:

Main-Class: <MainClassName>

This line must end with a newline.

For example---

  Step to create executablr jar filr ---

1. Create a new folder MyApp and put all the java files.
2. Now navigate to this folder from cmd and compile all files.( javac *.java)
3. Let we hava Main.java,Class1.java and Class2.java 
4. Write a manifest.txt file(write the statement  ,Main-Class: Main)
5. Now run the jar utility(jar cvfm myjar.jar manifest.txt *.class)
6. Now test your jar(myjar.jar)

How to create GUI in Java

In last post we have created a GUI. The basic to crate a GUI is consist of following steps.......

1.Create a class that extends JFrame/Jpanel/JApplet.

2.Create a default constructor, and a method void initComp() .In this method in first line set the layout of frame to null.

3.Call the initComp method in constructor, and in next line set the title of main window(this.setTitle("Title");) , then in next line set bounds, then set default close operation to EXIT_ON_CLOSE , then in next line setResizable.

4.Now write main method and write..(new <classname>().setVisible(true);).

5.Now your code is ready to run but this will only show a blank window.

6.To add component on this window firstly declare the objects of components. Now create a method for each component like..void myCompnent(). In this method first create object then set text,set bounds, set visible and then add to this frame. Now if you want to handle any event with this component write the event handler for the componet.

7.Now call these methods in the initComp method.

8.Now the code is complete you can use it.

The main problem in this code is to write event handler which I publish in next post.

Sample GUI class in Java

Java is specially designed for GUI programming. So we here start our chapter with making GUI........


To work with GUI we need a main window to work with. In Java we can use JFrame, JApplet, or JPanel  to create GUI. The best practice is to use JFrame.

Here we have a sample class which make a GUI with JFrame....

Sample GUI class in Java :

// package

        package mpc;

//  imports

    import java.awt.Color;

    import javax.swing.*;

    import java.awt.event.*;

// class extends jframe or jpanel

    public class App extends JFrame{

// constructors

    public App() {

    initComp();

    }

// main method

    public static void main(String[] args) {

    new App();

    }

// initComp method

    void   initComp() {

    this.myBtn();

    this.myLbl();

    this.setLayout(null);

    this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    this.setResizable(false);

    this.setBounds(10, 10, 300, 350);

    this.setVisible(true);

    }

// 1st component’s method

    void myBtn() {

    btn=new JButton();

    btn.setText("Click");

    btn.setBounds(5, 5, 100, 25);

    btn.setVisible(true);

    this.add(btn);

    btn.addActionListener(new ActionListener(){

    public void actionPerformed(ActionEvent e) {

    myBtnActionPerformed(e);}

    });

    }

// 1^st component’s event handler

    void  myBtnActionPerformed(ActionEvent e){

    lbl.setText("Hello.");

    }

// 2^nd component’s method

    void myLbl() {

    lbl=new JLabel();

    lbl.setText("");

    lbl.setBounds(7, 30, 100, 35);

    lbl.setVisible(true);

    this.add(lbl);

    }

// variable and component dec.

    JLabel lbl;

    JButton btn;

    }

//end of class
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Intro to Java

 To start learning java we have to know what java is ----


 The technologies that comes with Java can be classified in 5 categories :---

  1.Desktop Technologies

  2.Distributed Technologies

  3.Web Technologies

  4.Enterprise Technologies

  5.Micro Technologies
  
  To work with Desktop Technologies, Java provides Core Java and Advance Java(Java6).The scope of Desktop Technologies are in - Desktop Applications and LAN.
  
  To work with Distributed Technologies Java provides, RMI (Remote Method Invocation). The scope of Distributed Technologies are in - Distributed Storage and Distributed Processing.
  
  To work with Web Technologies, Java Provides Servlets, Java Server Pages (JSP), Java Server Faces (JSF). The scope of Web Technologies are in - Intranet, Extranet, and Internet.

  To work with Enterprise Technologies, Java Provides Enterprise Java Beans (EJB), Java Enterprise Edition (JEE). The scope of Enterprise Technologies is in Enterprise applications.
  
To work with Micro Technologies, Java Provides Java ME.The Scope of Micro Technologies are in - Mobile phones, Pagers, PDAs, Setup Boxes etc.


 To work on these technologies Java provides 3 Editions --

1. Java Standard Edition (Java SE)

• For Desktop and Distributed Apps.

2. Java Enterprise Edition (Java EE)

• For Web and Enterprise Apps.

3. Java Micro Edition (Java ME)

• For Micro Technologies

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