SASA JAVA

Map Reduce: Client program initiating the process

noreply@blogger.com (Unknown) — Thu, 06 Nov 2014 13:54:00 +0000

Map Reduce: Client program initiating the process

/**

* Program Starts */

package com.mapreduce.devx;

/**
 * Imports */

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.input.TextInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;

/**
 * Class */
public class DevXDriver { 
 public static void main(String[] args) throws Exception {  
 
  // Initiate configuration 
  Configuration configx = new Configuration();
   
  // Add resource files
  configx.addResource(new Path("/user/hadoop/core-site.xml"));
     configx.addResource(new Path("/user/hadoop/hdfs-site.xml"));
               
  // Create MapReduce job 
        Job devxmapjob = new Job(configx,"DevXDriver.class");
        devxmapjob.setJarByClass(DevXDriver.class);       
        devxmapjob.setJobName("DevX MapReduce Job");                  
       
     // Set output kay and value class
  devxmapjob.setOutputKeyClass(Text.class);
  devxmapjob.setOutputValueClass(Text.class);

  // Set Map class
  devxmapjob.setMapperClass(DevXMap.class);  
  
  // Set Combiner class
  devxmapjob.setCombinerClass(DevXReducer.class);  
  
  // Set Reducer class
  devxmapjob.setReducerClass(DevXReducer.class);     

  // Set Map output key and value classes
  devxmapjob.setMapOutputKeyClass(Text.class);
  devxmapjob.setMapOutputValueClass(Text.class);
       
  // Set number of reducer tasks
  devxmapjob.setNumReduceTasks(10);

  // Set input and output format classes
  devxmapjob.setInputFormatClass(TextInputFormat.class);
  devxmapjob.setOutputFormatClass(TextOutputFormat.class);
       
  // Set input and output path
  FileInputFormat.addInputPath(devxmapjob, new Path("/user/map_reduce/input/"));
  FileOutputFormat.setOutputPath(devxmapjob,new Path("/user/map_reduce/output"));       
  
  // Start MapReduce job
  devxmapjob.waitForCompletion(true);
 }
}

Sample Reduce function in JAVA (Part of Map reduce)

noreply@blogger.com (Unknown) — Thu, 06 Nov 2014 13:49:00 +0000

Sample Reduce function in JAVA (Part of Map reduce)

/**
* Program Starts
*/

package com.mapreduce.devx;
/**

* Imports 

*/


import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.URI;
import java.util.RandomAccess;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataOutputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Reducer;



/**

* Class 

*/



public class DevXReducer extends Reducer 
{   
 // Create variables for file path
    Path positive_file_path;
    Path negative_file_path;
    Path output_file_path;
    Path keyword_file_path;
    
    // Create variables for buffer
    BufferedReader positive_buff_reader;
    BufferedReader negative_buff_reader;
    BufferedReader keyword_buff_reader; 
    
    // Create variables for calculation
    static Double total_record_count=new Double("0"); 
   
    static Double count_neg=new Double("0");
    static Double count_pos=new Double("0");
    static Double count_neu=new Double("0");
   
    static Double percent_neg=new Double("0");
    static Double percent_pos=new Double("0");
    static Double percent_neu=new Double("0");

    Pattern pattrn_matcher;
    Matcher matcher_txt;
    static int new_row=0;
    FSDataOutputStream out_1st,out_2nd;  

 
  /**
  * @param key
  * @param values
  * @param context
  * @throws IOException
  * @throws InterruptedException
  */
    public void reduce(Text key, Iterable values,Context context) throws IOException, InterruptedException
     {           
     // Create configuration for reducer
     Configuration reduce_config = new Configuration();
     
        // Load hadoop config files
     reduce_config.addResource(new Path("/user/hadoop/core-site.xml"));
        reduce_config.addResource(new Path("/user/hadoop/hdfs-site.xml"));
     
        // Create variables
        String key_word = "";
        String check_keyword=key_word;  
        
     keyword_file_path=new Path("files/repository/keys.txt");
        FileSystem file_system_read = FileSystem.get(URI.create("files/repository/keys.txt"),new Configuration());
        keyword_buff_reader=new BufferedReader(new InputStreamReader(file_system_read.open(keyword_file_path)));
        
        FileSystem get_filesys = FileSystem.get(reduce_config);
  FileSystem get_filesys_posneg = FileSystem.get(reduce_config);
        
        Path path_output = new Path("/user/sentiment_output_file.txt");
        Path path_output_posneg = new Path("/user/posneg_output_file.txt");
        
        // Get keyword
        while(keyword_buff_reader.ready())
        {
         key_word=keyword_buff_reader.readLine().trim();
        
        } 
        
        // Check file system
        if (!get_filesys.exists(path_output)) {                       
            out_1st = get_filesys.create(path_output);
            out_2nd = get_filesys_posneg.create(path_output_posneg);
           
        }             
         
        // Check keyword matching using positive and negative dictionaries
        if(check_keyword.equals(key.toString().toLowerCase()))
        {      
         for(Text new_tweets:values)
            { 
             // Load positive word dictionary
    positive_file_path=new Path("/user/map_reduce/pos_words.txt");
                FileSystem filesystem_one = FileSystem.get(URI.create("files/pos_words.txt"),new Configuration());
                positive_buff_reader=new BufferedReader(new InputStreamReader(filesystem_one.open(positive_file_path)));
              
                // Load negative word disctinary
                negative_file_path = new Path("/user/map_reduce/neg_words.txt");
                FileSystem filesystem_two = FileSystem.get(URI.create("files/neg_words.txt"),new Configuration());
                negative_buff_reader =new BufferedReader(new InputStreamReader(filesystem_two.open(negative_file_path)));

                ++total_record_count;

                boolean first_flag=false;
                boolean second_flag=false;

                String all_tweets=new_tweets.toString();              
                String first_regex = "";
                String second_regex = "";

                while(positive_buff_reader.ready())
                {
                    first_regex=positive_buff_reader.readLine().trim();
                    new_row++;           
                    pattrn_matcher = Pattern.compile(first_regex, Pattern.CASE_INSENSITIVE);
                    matcher_txt = pattrn_matcher.matcher(all_tweets);
                    first_flag=matcher_txt.find();

                    if(first_flag)
                    {  
                     out_2nd.writeBytes(all_tweets);
                        context.write(new Text(first_regex),new Text(all_tweets));                  
                        break;
                    }       
                }
                while(negative_buff_reader.ready())
                {
                    new_row++;                    
                    second_regex=negative_buff_reader.readLine().trim();
                    pattrn_matcher = Pattern.compile(second_regex, Pattern.CASE_INSENSITIVE);
                    matcher_txt = pattrn_matcher.matcher(all_tweets);
                    second_flag=matcher_txt.find();
                    if(second_flag)
                    {                     
                     out_2nd.writeBytes(all_tweets);
                        context.write(new Text(second_regex),new Text(all_tweets));
                        break;
                    }

                }
                if(first_flag&second_flag)
                {
                    ++count_neu;
                }
                else
                {
                    if(first_flag)
                    {
                        ++count_pos;
                    }
                    if(second_flag)
                    {
                        ++count_neg;
                    }
                    if(first_flag==false&second_flag==false)
                    {
                        ++count_neu;
                    }
                }
                // Close buffers
                negative_buff_reader.close();
                positive_buff_reader.close();

            }
         
         // Calculate percent values
            percent_pos=count_pos/total_record_count*100;
            percent_neg=count_neg/total_record_count*100;
            percent_neu=count_neu/total_record_count*100;

          try{           
    // Write to the files
             out_1st.writeBytes("\n"+key_word);
    out_1st.writeBytes(","+total_record_count);
    out_1st.writeBytes(","+percent_neg);
    out_1st.writeBytes(","+percent_pos);
    out_1st.writeBytes(","+percent_neu);
    
    // Close file systems
    out_1st.close();
    get_filesys.close();
          }catch(Exception e){
           e.printStackTrace();
          } 
        }        
    }
}

Sample Map Function in JAVA (Part of Map Reduce)

noreply@blogger.com (Unknown) — Thu, 06 Nov 2014 13:45:00 +0000

Map function splitting the data into chunks

/**

*Program Starts

package com.mapreduce.devx;
/**

*Import Functions

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.URI;
import java.util.StringTokenizer;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;
/**

*Class

public class DevXMap extends Mapper {

// Create Path, BufferedReader and Text variables
Path file_path;
BufferedReader buffer_reader;
Text tweet_values = new Text();
/**
* @param key
* @param value
* @param context
*/

public void map(LongWritable key, Text value, Context context) {
try{

// Create configuration for Map
Configuration map_config = new Configuration();

// Load Hadoop core files in configuration
map_config.addResource(new Path("/user/hadoop/core-site.xml"));
map_config.addResource(new Path("/user/hadoop/hdfs-site.xml"));

        // Create variables
        String searchkeyword = "";

// Open file from the file path
file_path=new Path("files/repository/keys.txt");
            FileSystem file_system = FileSystem.get(URI.create("files/repository/keys.txt"),new Configuration());

// Load buffer reader
            buffer_reader=new BufferedReader(new InputStreamReader(file_system.open(file_path)));

            while(buffer_reader.ready())
            { searchkeyword=buffer_reader.readLine().trim(); }

            // Get key value
            final Text key_value = new Text(searchkeyword);

            // Check value and take decision
            if(value == null)
{
return;
}
else{
StringTokenizer string_tokens = new StringTokenizer(value.toString(),",");
int count = 0;

while(string_tokens.hasMoreTokens()) {
count ++;
if(count <=1)
continue;

String new_tweet_value = string_tokens.nextToken().toLowerCase().trim().replaceAll("\\*","");

if(new_tweet_value.contains(searchkeyword.toLowerCase().trim())) {
tweet_values.set(new_tweet_value);
context.write(key_value,tweet_values);
}
}
}
}
catch(Exception e){
e.printStackTrace();
}
}
}

Border Layout

noreply@blogger.com (Unknown) — Thu, 08 Jul 2010 11:36:00 +0000

BorderLayout divides the container into five Geographical regions namely
North,South,East,West and Center.This is very commonly used Lyout
Manager.You can add at most one component to each region of a BorderLayout.
To put more than one component in a section, put them in a JPanel (with its own layout),
then add that panel to the border layout.
When you add components to a container which uses BorderLayout, specify the target region as the second parameter as, for example, BorderLayout.SOUTH.
If nothing is added to a region then neighbouring regions go on to fill up space.

Construcors:-
new BorderLayout();
new BorderLayout(int hgap,int vgap);

Example
Source Code:-
import javax.swing.*;
import java.awt.*;

class borderlayout extends JFrame{
public static void main(String a[]){
//initializing frames
JFrame jf=new JFrame("BorderLayout");
JFrame jf1=new JFrame("BorderLayout");
//initializing panels
JPanel panel=new JPanel();
//initializing buttons
JButton jbn=new JButton("North");
JButton jbs=new JButton("South");
JButton jbe=new JButton("East");
JButton jbw=new JButton("West");
JButton jbc=new JButton("Central");
//setting up layout
panel.setLayout(new BorderLayout());
panel.add(jbn,BorderLayout.NORTH);
panel.add(jbs,BorderLayout.SOUTH);
panel.add(jbe,BorderLayout.EAST);
panel.add(jbw,BorderLayout.WEST);
panel.add(jbc,BorderLayout.CENTER);
//adding to frame
jf.getContentPane().add(panel);
jf.setSize(250,200);
jf.setVisible(true);
}
}

Card Layout Manager

noreply@blogger.com (Unknown) — Thu, 08 Jul 2010 11:35:00 +0000

One of the most complex Layout Manager is Card Layout manager.Using this manager you can create a stack of cards and flip from one layout to another.This type of organization is similar to tabbed dialogs.Card Layout provides following

Costructors:-

public CardLayout(); //Constructor creates new CardLayout

public CardLayout(int hgap,int vgap);//Constructor creates a new card layout with specified horizontal and vertical gap.

To Create a Card Layout Manager with card layout manager object,you first create a parent panel to hold the cards .Then you create an object of the CardLayout class and set it as the layout manager of the panel.Finally ,you add each card to the layout by creating the component and adding the to the panel.

Following are the methods to switch between cards that are in stack of layout.

1.void first(Container parent) //Display first card
2.void last(Container parent) //Display last card
3.void next(Container parent) //Display next card
4.void previous(Container parent) //Display previous card
5.void first(Container parent,String name) //Display specified card

Example
code snippet:-

/*
CardLayout c1;
JPanel panel;
JButton jb 1;
cardlayout()
{
JFrame jf1=new JFrame("Card Layout demo");
JPanel panel=new JPanel();
JButton jb1=new JButton("Next Button>>");
JButton jb2=new JButton("Last Button>>");
CardLayout c1=new CardLayout();
panel.setLayout(c1);
panel.add("button1",jb1);
panel.add("button2",jb2);
jb1.addActionListener(this);
jb2.addActionListener(this);
jf1.getContentPane().add(panel);
jf1.setVisible(true);
jf1.setSize(200,200);
}
public void actionPerformed(ActionEvent ae)
{
c1.next(panel);

}*/

Grid Bag Layout

noreply@blogger.com (Unknown) — Thu, 08 Jul 2010 11:35:00 +0000

The GridBag Layout manager is the most flexible and complex layout manager that the AWT provides. It places components in rows and columns allowing specific components by assigning weights to individual components in the gridbag layout.

When you specify the size and position of components,you also need to specify the constraint for each component.To specify constraint ,you need to set the variables in GridBagConstraints Object and specify theGridBagLayout manager object with the setConstraint() method, to associate the constraint with the component.

The GridBagLayout class has a single constructor that does not take any arguments.Since the position of each component in a layout is controlled by a GridBagLayout object and is determined by the currently setGridBagConstraints object,you need to create the GridBagConstraintsobject before the layout can be built.

GridBagLayout g=new GridBagLayout();
GridBagConstraints cons=new GridBagConstraints();

You can assign following values to GridBagConstraints attributes:-

anchor:-It is used when the component is smaller than its display area to determine where to place the compoenent.valid values are shown below:

GridBagConstraints.CENTER
GridBagConstraints.NORTH
GridBagConstraints.NORTHEAST
GridBagConstraints.EAST
GridBagConstraints.SOUTHEAST
GridBagConstraints.SOUTH
GridBagConstraints.SOUTHWEST
GridBagConstraints.WEST
GridBagConstraints.NORTHWEST

fill:- It is used when the display area of component is larger than the requested size of the component to determine whether to resize the component.valid values are:-
GridBagConstraints.NONE
GridBagConstraints.HORIZONTAL
GridBagConstraints.VERTICAL
GridBagConstraints.BOTH

gridwidth,gridheight:-It specifies number of columns or rows in display area of components the default value is 1,valid values are:
GridBagConstraints.REMAINDER
GridBagConstraints.RELATIVE

gridx,gridy:-They specify the row and column at the upper left of the components display area.The leftmost column has the address gridx=0 and topmost cell has the address gridy=0.

insets:- They specify the extenal padding of the component ,that is ,the minimum amount of space between the components and the edges of its display area.The value is specified as an Insets object .By default ,each component does not have external padding.The default padding value is insets(0,0,0,0).

ipadx,ipady:-They specify the internal padding to be added to the minimum size of the component.The default value is 0.The width of the component will be its minimum width plus ipadx*2 pixels.Similarly ,the height of the component will be its minimum height plus ipady*2 pixels.

weightx,weighty:- They determine whether the component stretch horizontally to fill the display area of the applet or vertically.The default value is 0 for both.

Example
Source code:-

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;

public class GridBagWindow extends JFrame {
boolean inAnApplet = true;
final boolean shouldFill = true;
final boolean shouldWeightX = true;

public GridBagWindow() {
JButton button;
Container contentPane = getContentPane();
GridBagLayout gridbag = new GridBagLayout();
GridBagConstraints c = new GridBagConstraints();
contentPane.setLayout(gridbag);
if (shouldFill) {
//natural height, maximum width
c.fill = GridBagConstraints.HORIZONTAL;
}

button = new JButton("Button 1");
if (shouldWeightX) {
c.weightx = 0.5;
}
c.gridx = 0;
c.gridy = 0;
gridbag.setConstraints(button, c);
contentPane.add(button);

button = new JButton("2");
c.gridx = 1;
c.gridy = 0;
gridbag.setConstraints(button, c);
contentPane.add(button);

button = new JButton("Button 3");
c.gridx = 2;
c.gridy = 0;
gridbag.setConstraints(button, c);
contentPane.add(button);

button = new JButton("Long-Named Button 4");
c.ipady = 40; //make this component tall
c.weightx = 0.0;
c.gridwidth = 3;
c.gridx = 0;
c.gridy = 1;
gridbag.setConstraints(button, c);
contentPane.add(button);

button = new JButton("Button 5");
c.ipady = 0; //reset to default
c.weighty = 1.0; //request any extra vertical space
c.anchor = GridBagConstraints.SOUTH; //bottom of space
c.insets = new Insets(10,0,0,0); //top padding
c.gridx = 1; //aligned with button 2
c.gridwidth = 2; //2 columns wide
c.gridy = 2; //third row
gridbag.setConstraints(button, c);
contentPane.add(button);

addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {
if (inAnApplet) {
dispose();
} else {
System.exit(0);
}
}
});
}

public static void main(String args[]) {
GridBagWindow window = new GridBagWindow();
window.inAnApplet = false;

window.setTitle("GridBagLayout");
window.pack();
window.setVisible(true);
}
}

JButton

noreply@blogger.com (Unknown) — Thu, 08 Jul 2010 11:34:00 +0000

JButton

Jbutton is the standrad command button used in Java.It is mainly used for event driven programming.A JButton when clicked fires an event which is handled by an event handler which in response do some work as indicated in hadler.On click the JButton takes some set of input and process that.The JButton is a Swing Component.

JButton Class has following constructors:-

JButton() // Creates a button with no text or icon

JButton(Action a) //Creates a button where are properties are tak

en from action supplied

JButton(Icon icon)//Creates a button with a icon

JButton(String text)//Creates a button with some text

JButton(String text ,Icon icon)//Creates button with both text and icon

Features of JButton:-

1.JButton applies event handling.

2.JButton has a different look and feel for enabled and disabled buttons.

3.You can set mnemonics for JButtons.

4.TooltipText can also be set for JButtons.

Following example shows the application of all above mentioned features:-
In this example there are buttons which on click disable and enable the corresponding buttons.
The program follows:-

import javax.swing.*;

import java.awt.event.*;

public class ButtonDemo extends JPanel

implements ActionListener {

protected JButton but1, but2, but3;

public ButtonDemo() {

ImageIcon leftButtonIcon = createImageIcon("d:/image/left.gif");

ImageIcon middleButtonIcon = createImageIcon("c:/image/middle.gif");

ImageIcon rightButtonIcon = createImageIcon("c:/image/right.gif");

but1 = new JButton("Disable middle button", leftButtonIcon);

but1.setActionCommand("disable");

//setting up mnemonics

but1.setMnemonic(KeyEvent.VK_D);

but2 = new JButton("Middle button", middleButtonIcon);

but2.setMnemonic(KeyEvent.VK_M);

but3 = new JButton("Enable middle button", rightButtonIcon);

//Use the default text position of CENTER, TRAILING (RIGHT).

but3.setMnemonic(KeyEvent.VK_E);

but3.setActionCommand("enable");

//enabling the command button

but3.setEnabled(false);

//Listeners for actions on buttons 1 and 3.

but1.addActionListener(this);

but3.addActionListener(this);

but1.setToolTipText("Click this button to disable the middle button.");

but3.setToolTipText("Click this button to enable the middle button.");

//Add Components to this container, using the default FlowLayout.

add(but1);

add(but2);

add(but3);

}

public void actionPerformed(ActionEvent e) {

if ("disable".equals(e.getActionCommand())) {

but2.setEnabled(false);

but1.setEnabled(false);

but3.setEnabled(true);

} else {

but2.setEnabled(true);

but1.setEnabled(true);

but3.setEnabled(false);

}

/** Returns an ImageIcon, or null if the path was invalid. */

protected static ImageIcon createImageIcon(String path) {

java.net.URL imgURL = ButtonDemo.class.getResource(path);

if (imgURL != null) {

return new ImageIcon(imgURL);

} else {

System.err.println("Couldn't find file: " + path);

return null;

}

// Create the GUI.

private static void createAndShowGUI() {

//Create and set up the JFrame.

JFrame frame = new JFrame("ButtonDemo");

frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

//Create and set up the content pane.

ButtonDemo newContentPane = new ButtonDemo();

newContentPane.setOpaque(true); //content panes must be opaque

frame.setContentPane(newContentPane);

//Display the JFrame.

frame.pack();

frame.setVisible(true);

}

public static void main(String[] args) {

//creating and showing this application's GUI.

javax.swing.SwingUtilities.invokeLater(new Runnable() {

public void run() {

createAndShowGUI();

}

});

}

JLabel

noreply@blogger.com (Unknown) — Thu, 08 Jul 2010 11:34:00 +0000

JLabels in Swing can contain text, images or both.
JLabel do not generate an action event though
it works on Mouse Events.Like MouseMotion,MouseListener etc.
We can also add non-functional labels in our interface(GUI).
You can also specify the position of the text relative to the image.
Also we can align,specify border,size and many more properties.
Constructors:-JLabel class has following Constructors

JLabel() // Creates a JLabel without an image and with empty string title
JLabel(Icon icon) //Creates a JLabel instance with specified image as title
JLabel(Icon image,int horizontalAlignment)// Creates a JLabel object with image and alignment
JLabel(String text)//JLabel with some text as title
JLabel(String text,Icon image,int horizontalAlignment)
JLabel(String text ,int horizontalalignment)
Example:-
The following exmaple is for simple label showing only text:-

import javax.swing.*;

public class SimpleJLabel extends JFrame{

public static void main(String[] args) {

JLabel label = new JLabel("A Simple Text Label");

JFrame frame = new JFrame();

frame.getContentPane().add(label);

frame.pack();

frame.setVisible(true);
}
}
Example:-
The Following Example shows setting up an Icon on Label

import javax.swing.*;

public class SimpleJLabel extends JFrame{

public static void main(String[] args) {

JLabel label = new JLabel();

label.setIcon(new ImageIcon("e1.png"));

JFrame frame = new JFrame();

frame.getContentPane().add(label);

frame.pack();

frame.setVisible(true);

}

}

You can also set many more properties like mnemonics,tooltiptext alignment etc.

JTextField

noreply@blogger.com (Unknown) — Thu, 08 Jul 2010 11:33:00 +0000

JTextField

A text field is a basic text control that enables the user to type a small amount of text.

The text field is editable. It is handy in cases

where a single line of input is required or a little information is neede.

It is mostly used in forms and does most work on Event handling.There are certain methods which copies the contents of TextField whenever an action is fired.

Constructors:-

JTextField has four types of constructors which are as follows

1.JTextField()

2.JTextField(String) //Creates a TextField with initial text as String

3.JTextField(String,int) //creates a TextField with length of cloumn being chars and default text is as String

4.JTextField(int) //creates s TextField with length of column being chars.

Note: Always try to specify the number of columns for each text field. If you do not specify the number of columns or a preferred size, then the field's preferred size changes whenever the text changes, which can result in unwanted layout changes.

Example:-Creating a form with JTextField

//textfield.java

import javax.swing.*;

class textfield extends JFrame{

public static void main(String a[]){

JFrame frame=new JFrame("JTextFieldDemo");

JPanel panel=new JPanel();

JTextField txt=new JTextField(10);

JTextField txtf=new JTextField("Default",20); //with default text written and size of 20

panel.add(txt);

panel.add(txtf);

frame.getContentPane().add(panel);

frame.setVisible(true);

frame.pack();

}

We have several methods for getting and setting values from and to JTextField

1.String getText()

2.void setText(String)

Edit methods of JTextField component

1.void setEditable(boolean) //set whether the text in the JTextField is editable or not

2. boolean isEditable() //returns whether the tetfield is editable or not

For setting and getting the width of JTextField use

void setColumns(int) //specifies the width of textfield

int getColumns() //obtains number of columns of the TextField

For selecting whole field at once use following

void selectAll()

For adding ActionListeners use following

void addActionListener(ActionListener) //adds action listener

void removeActionListener(ActionListener) //removes ActionListener

Setting ToolTip and Icon

noreply@blogger.com (Unknown) — Thu, 08 Jul 2010 11:32:00 +0000

Adding Icons and ToolTips

Tooltips are shot information messages which are displayed when your mouse pointer rests at some components.That is if suppose your mose pointer is at a button whose tooltiop is set as "click here" the if your pointer comes over button the a small message will appear saying "click here".

For setting ToolTip we can use setToolTipText() method of JComponent class.

ToolTip Example:-

// tooltip.java

import javax.swing.*;
public class tooltip
{
public static void main(String a[])
{
JFrame frm=new JFrame("ToolTip Demo");
JPanel panel=new JPanel();
JLabel labeltool=new JLabel("ToolTio DemoPlace mouse over it");
labeltool.setToolTipText("This is ToolTip");
panel.add(labeltool);
frm.getContentPane().add(panel);
frm.setVisible(true);
frm.pack();
}
}

SettingIcon Example:-

// settingicon.java

import java.awt.*;
import javax.swing.*;
public class settingicon
{
public static void main(String a[])
{
JFrame frm=new JFrame("Setting Icon Demo");
JPanel panel=new JPanel();
JLabel label=new JLabel(new ImageIcon("BAK.png"));
panel.add(label);
frm.getContentPane().add(panel);
frm.setVisible(true);
frm.pack();
}
}

Setting Mnemonics and Shortcut Keys

noreply@blogger.com (Unknown) — Thu, 08 Jul 2010 11:32:00 +0000

Setting a Shrotcut Key(Mnemonic)

A shortcut key is an underlined character you may in labels,buttons,menus etc.These are called as mnemonics.You can select a control by pressing the combination of Alt key and the character.For example if underlined character is 's' then in order to activate control press Alt+s.You can set mnemonic by using setMnemonic(Char ch)

Syntax:-

component.setMnemonic(Char ch);

Exapmle:-
In the Screen shot the mnemonic is set as 'M'.
So this button can be activated by pressing Alt+M.
// memonic.java

import java.awt.*;
import javax.swing.*;
public class mnemonic
{
public static void main(String a[])
{
JFrame frm=new JFrame("Mnemonic Demo");
JPanel panel=new JPanel();
JButton Button=new JButton("Setting Mnemonic");
Button.setMnemonic('M');
panel.add(Button);
frm.getContentPane().add(panel);
frm.setVisible(true);
frm.pack();
}
}

DropDown Menu or Choice menu

noreply@blogger.com (Unknown) — Thu, 08 Jul 2010 11:32:00 +0000

DropDown Menu or The Choice class

A choice menu is a dropdown menu which upon clicking presents a list of menus(choices) from which user may choose one.That is when a user clicks on the choice control a list of option drops down from which a user can select only one choice.It enforces user to choose from the list of options provided.

Constructor:-

// Choice();
creating an object of Choice class
e.g. Choice choice=new Choice();

Adding Items:-

Items in the list of menu are added by using addItem(String Item) method.
e.g. choice.addItem("Option 1");

Example:-
//choice.java

import java.awt.*;

public class choice
{
public static void main(String a[])
{
Frame frm=new Frame("Choice menu demo");
Panel panel=new Panel();
Choice choice=new Choice();
frm.add(panel);
choice.addItem("Option 1");
choice.addItem("Option 2");
choice.addItem("Option 3");
choice.addItem("Option 4");
panel.add(new Label("This is DropDown MENU"));
panel.add(choice);
frm.show();
frm.pack();
frm.setBounds(100,100,250,200);
}
}

Useful Methods of Choice Class:-

How to create and use Check Boxes

noreply@blogger.com (Unknown) — Thu, 08 Jul 2010 11:31:00 +0000

CheckBox is a unique java control which lets user select one or more options.This control becomes handy where some sort of selection is to be made.I will explain here the CheckBoxes In Java Swings.Which are created using JCheckBox class.

Constructors:-There are five constructors of CheckBox

1.Checkbox() --> Creates a check box with an empty string for its label.

2.Checkbox(String label, boolean state) --> Creates a check box with the specified label and sets the specified state.

3.Checkbox(String label) --> Creates a check box with the specified label.

4.Checkbox(String label, boolean state, CheckboxGroup group) --> Constructs a Checkbox with the specified label, set to the specified state, and in the specified check box group.

5.Checkbox(String label, CheckboxGroup group, boolean state) --> Creates a check box with the specified label, in the specified check box group, and set to the specified state.

Example:-This simple swing example illustrates how checkboxes are added.

//test.java

import javax.swing.*;

public class test{
public static void main(String[] args){
JFrame frame = new JFrame("Check Box Frame");
JCheckBox chkop1 = new JCheckBox("option 1");
JCheckBox chkop2 = new JCheckBox("option 2");
JCheckBox chkop3 = new JCheckBox("option 3");
JPanel panel=new JPanel();
panel.add(chkop1);
panel.add(chkop2);
panel.add(chkop3);
frame.getContentPane().add(panel);
frame.pack();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
}

Selecting Checkboxes:-In this example the checkboxes are default selected using setSelected(boolean state) method of JCheckBox class.

//test1.java

import javax.swing.*;

public class test{
public static void main(String[] args){
JFrame frame = new JFrame("Check Box Frame");
JCheckBox chkop1 = new JCheckBox("option 1");
chkop1.setSelected(true);
JCheckBox chkop2 = new JCheckBox("option 2");
chkop2.setSelected(true);
JCheckBox chkop3 = new JCheckBox("option 3");
JPanel panel=new JPanel();
panel.add(chkop1);
panel.add(chkop2);
panel.add(chkop3);
frame.getContentPane().add(panel);
frame.pack();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
}

Other useful methods:-

setLabel() :-Sets Label as provided string to this CheckBox.
getLabel() :-Returns Label of CheckBox.
addItemListener() :-Only ItemListeners can be added to CheckBox control for event handling purposes.

How to Use CheckBoxGroup

noreply@blogger.com (Unknown) — Thu, 08 Jul 2010 11:30:00 +0000

CheckboxGroup class is used to group togather the Checkboxes,from which only one can be selected at a time.
That is exactly one Checkbox in that goup will be "on" else remain "false".By clicking on Checkbox we may "on" or "off" the desired Checkbox.This control is mostly used in making selection ,where exactly one selection is needed form given choices.

more on Checkboxes Visit Checkbox Tutorial
Constructor:-

CheckboxGroup() ---> Creates a new instance of CheckboxGroup.
Important Methods:-

void getSelectedCheckbox() ----> Gets the current choice from this check box group.
void setSelectedCheckbox(Checkbox cb) ----> Turn "on" the specified CheckBox.
How to Use CheckboxGroup:-

Example:-

// test.java

import javax.swing.*;
import java.awt.*;

public class test{
public static void main(String[] args){
JFrame frame = new JFrame("Check Box Frame");
CheckboxGroup cb=new CheckboxGroup();
Checkbox chkop1 = new Checkbox("option1",false,cb);
Checkbox chkop2 = new Checkbox("option2",false,cb);
Checkbox chkop3 = new Checkbox("option3",true,cb);
JPanel panel=new JPanel();
panel.add(chkop1);
panel.add(chkop2);
panel.add(chkop3);
frame.getContentPane().add(panel);
frame.pack();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
}

Using JTextField and JTextArea

noreply@blogger.com (Unknown) — Thu, 08 Jul 2010 11:30:00 +0000

TextFields are used to take input from user also it can be used to display results.
The various constructors and methods are defined in the previous JTextField tutorials.

Values from a TextField is extracted using String getText() and set usingvoid setText(String txt).
The user can select a portion from the JTextField and JTextArea usingString getSelectedText() and void select(int start_index,int end_index)
String getSelectedText() retrurns the String portion selected by the user from the textfield.
You can also enable or disable the TextField that is if you want TextField to be editable the use the methos void setEditable(boolean value) to true else set false.If you want to get value of editable TextField useboolean isEditable().

Sometimes you wish to set a password field in which the entered character must not be shown.It has to be replaced by some other sign or value.To set a password field you must use void setEchoChar(Char ch)character you specified in 'ch' will be shown when some charater is typed.
If you want to get the Charcter specified the use char getEchoChar().
Example :-
getting selected value from a text field and displaying it to other and use of Password field.

// textfield.java

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class textfield extends JFrame implements ActionListener
{
JFrame frame;
JPanel panel;
JTextField txtname,txtdisplay;
TextField txtpass;
JButton button;
public textfield()
{
frame=new JFrame("Text Field usage demo");
panel=new JPanel();
txtname=new JTextField(25);
txtpass=new TextField(25);
txtpass.setEchoChar('#');
txtdisplay =new JTextField(25);
JButton button=new JButton("Display selected");
button.addActionListener(this);
panel.setLayout(new GridLayout(3,2));
panel.add(new JLabel("Name :"));
panel.add(txtname);
panel.add(new JLabel("Password :"));
panel.add(txtpass);
panel.add(txtdisplay);
panel.add(button);
frame.getContentPane().add(panel);
frame.show();
frame.pack();

}

public void actionPerformed(ActionEvent ae)
{

txtdisplay.setText("Name :"+txtname.getSelectedText()+" Pass :"+txtpass.getText());

}
public static void main(String a[])
{
new textfield();
}
}

Example:-
getting selected value from a text area and displaying selected in textfield.

// textarea.java

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class textarea extends JFrame implements ActionListener
{
JFrame frame;
JPanel panel;
JTextField txtname,txtdisplay;
TextField txtpass;
JTextArea area;
JButton button;
public textarea()
{
frame=new JFrame("Text Area usage demo");
panel=new JPanel();
txtdisplay =new JTextField(25);
area = new JTextArea("vaibhav pandey has made this programme",5,5);
JButton button=new JButton("Display selected");
button.addActionListener(this);
panel.add(area);
panel.add(txtdisplay);
panel.add(button);

frame.getContentPane().add(panel);
frame.show();
frame.pack();

}

public void actionPerformed(ActionEvent ae)
{
txtdisplay.setText("Selected String :"+area.getSelectedText());
}
public static void main(String a[])
{
new textarea();
}
}.

Loading Image on JFrame using JFileChooser

noreply@blogger.com (Unknown) — Thu, 08 Jul 2010 11:30:00 +0000

JFileChooser is a very handy utility in java Swings to choose any particular file of an extension.
Sometimes in our applications we need to load images onto our main container .In java we can use either JFrame or JPanel to load images.Statically we can provide the path of image into our program,but most of times it is not feasible for us to give image path statically.For specifying image path dynamically we use JFileChooser which returns path of a selected image.You can also select the desierd file extensions for whom you are looking.In following Example it is elaborated how to use JFileChooser and using it how we can load an image on a container.

Example (Source code ):-

//imageloading.java

//Program developed by Vaibhav Pandey

import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.sql.SQLException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;

public class imageloading extends JFrame
{
BufferedImage mImage;
String name,name1;
public imageloading()
{
JFrame frm=new JFrame("image loading test");
String source=filechoose();
File inputFile = new File(source);
try {
mImage = ImageIO.read(inputFile);
} catch (IOException ex) {
//Logger.getLogger(index.class.getName()).log(Level.SEVERE, null, ex);
}
JLabel lb=new JLabel(new ImageIcon(mImage));
frm.getContentPane().add(lb);
frm.show();
frm.pack();
}

String filechoose()
{
JFileChooser chooser = new JFileChooser();
chooser.setCurrentDirectory(new File("."));

chooser.setFileFilter(new javax.swing.filechooser.FileFilter() {
public boolean accept(File f) {
name = f.getName().toLowerCase();
return name.endsWith(".gif") || name.endsWith(".jpg")
|| name.endsWith(".jpeg") || f.isDirectory();
}

public String getDescription() {
return "Image files";
}
});

int r = chooser.showOpenDialog(this);

if (r == JFileChooser.APPROVE_OPTION) {
name1 = chooser.getSelectedFile().getAbsolutePath();
StringBuffer sb=new StringBuffer();
sb.append(name1);

int l=sb.length();
for(int i=0;i
{
if(sb.charAt(i)=='\\')
{
sb.insert(i, "\\");i++;
}
}
}
return name1;
}
public static void main(String a[])
{
new imageloading();
}
}

Output Windows:-

Following first widow shows the JFileChooser() instance opened and asking to
select a file of given extension,and in second window you can see the loaded image.

Elaboration:-In the given code we have used the ImageIO class to read the image file whose file is being specified and consequently is buffered.Later this buffered image is set on a Label as a ImageIcon to display it on the frame.

JFileChooser() is used to choose the files of desired extension here FileFilter() method is used to filter the files on the basis of extensions .Here we have considered only .jpeg and .gif images.Since the '/' is treated as a escape sequence in Java thus in when we are fetching path name in variable 'name1' using method 'JFileChoose.getSelectedFile().getAbsolutePath()' ,in order to omit the escape sequence we embed '//' in the path when we have some path selected.

We have used 'JFileChooser.APPROVE_OPTION' because to verify that we have selected a legitimate file or not.Any queries and comments are most welcome.In Java JFileChooser is a nice utility ,use it and tell me about the tutorial.

Menus In Java Swings

noreply@blogger.com (Unknown) — Thu, 08 Jul 2010 11:29:00 +0000

Every window can have a menu associated with it.Menu Bars basic function is to provide a list of choices.Each choice has its own drop-down menu(is provided otherwise none).This is implemented in Java by using following classes:-

MenuBar
Menu
MenuItem
CheckboxMenuItem

A menu bar can contains many menu objects.Each menu object may contain many MenuItem objects.In this implementation it is also possible to include checkable menu items.These can be implemented by CheckboxMenuItem class and will place a check mark next to them when they get selected.

First look at the constructors involved in creation of a menubar application.

1. MenuBar:-MenuBar is the highest class in this application and it will contain all the menu's inside it.It has only default constructor.

//MenuBar () only default constructor

2.Menu:-The constructors for Menu is as following.Menu's object will hold menu item's in them.

//Menu()
//Menu(String optionName)
//Menu(String optionName,boolean Removable)

In this case optionName provides the name of menu selection.If removable are set to true then menu can be removed and allowed to roam free.Otherwise it will remain with the menu bar.

3.MenuItem:-The Individual menuitems are of type MenuItem .These controls are to be placed on Menu object.

//MenuItem()
//MenuItem(String itemName)
//MenuItem(String itemName,MenuShortcut key)

here itemName is the name of item shown on menu and key is the menu shortcut for this item.

4.CheckboxMenuItem:-CheckboxMenuItem creates the checkboxes which can be placed as a menu and show their state by checked or unchecked.

//CheckboxMenuItem()
//CheckboxMenuItem(String itemName)
//CheckboxMenuItem(String itemName,boolean on)

itemName refers to the name of checkbox displayed on menu and on refers its state checked or unchecked.

Important Methods:-There are methods with various functionality lets see

1.void setEnabled(boolean flagvalue):-This method sets any menuitem to enabled or disabled state.Which specifies whether the menuitem is active or not(Click works or not).

2.boolean isEnabled():-This method returns the value whether the menuitem is active or inactive.That is either true or false.

3.void setLabel(String newName):-This method changes the name of a menuitem.

4.String getLabel():-It returns the name of the menuitem.

5.boolean getState():-This method returns the value (checked or unchecked) of
CheckboxMenuItem object.

6.void setState(boolean checked):-You can set the value of CheckboxMenuItem to true or false using this method.

How to create MenuBar Steps

noreply@blogger.com (Unknown) — Thu, 08 Jul 2010 11:28:00 +0000

How to create Menu and MenuBars Step wise procedure

1.Create an object of MenuBar class:MenuBar can be attached a Frame and it will be displayed just below the title bar.
MenuBar mb=new MenuBar();

2.Call the method setMenuBar(MenuBar):-This method is used to attach the MenuBar to a Frame.
setMenuBar(mb);

3.Create objects of the Menu class for each menu you want to add on menu bar.

Menu file=new Menu("File");
Menu edit=new Menu("Edit");
Menu help=new Menu("Help");

4.Call add() method of MenuBar class to add each menu object to the menu.

mb.add(file);
mb.add(edit);
mb.add(help);

5.Create object ofMenuItem orCheckboxMenuItem class for each sub menu item.

MenuItem save =newMenuItem("Save");
MenuItem newf =newMenuItem("New");
MenuItem open =new MenuItem("Open");
CheckboxMenuItem cbm=new CheckboxMenuItem("check");

6.Call add() method of Menu class to add each menu item to its appropriate menu.

file.add(newf);
file.add(open);
file.add(save);

Complete Example :-

Source Code:-
//MyMenubar.java

import java.awt.*;
public class MyMenubar
{
public static void main(String a[])
{
Frame frame=new Frame("MenuBar Demo");
MenuBar mb=newMenuBar();
frame.setMenuBar(mb);
Menu file=new Menu("File");
Menu edit=new Menu("Edit");
Menu help=new Menu("Help");
Menu options=new Menu("Options");
mb.add(file);
mb.add(edit);
mb.add(help);
MenuItem save =new MenuItem("Save");
MenuItem newf =new MenuItem("New");
MenuItem open =new MenuItem("Open");
CheckboxMenuItem cbm=new CheckboxMenuItem("check");
file.add(newf);
file.add(open);
file.add(save);
file.add(options);
options.add(newMenuItem("Font"));
options.add(newMenuItem("Size"));
options.add(newMenuItem("Color"));
edit.add(cbm);
cbm.setState(true);
cbm.setEnabled(false);
open.setEnabled(false);
frame.setVisible(true);
frame.setSize(300,300);
}
}

How to create pop-up menus in Java

noreply@blogger.com (Unknown) — Thu, 08 Jul 2010 11:28:00 +0000

Pop-up menus are the menus that are displayed when a user clicks the right mouse button.They are sometimes also known as short-cut menus.
Short cut menus are very handy in cases where some functionality you want to provide like adding a help menu to all controls on right click.

Step for creating Pop-up menus:-

1.Create an object of the JPopupMenu class.
2.Create object of the Menu class for each menu you want to add on the menu bar.
3.Call the add() method of the JPopupMenu class to add each menu object to the pop-up menu.
4.Create objects of the JMenuItem or CheckboxMenuItem class for each item that you want to in the menu.
5.Call the add() method of the Menu class to add each item to its appropriate menu.

Example Source code:-

//PopUpColorMenu.java
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class PopUpColorMenu
{
Component selectedComponent;

public PopUpColorMenu( ) {
JFrame frame = new JFrame("PopUpColorMenu v1.0");

final JPopupMenu colorMenu = new JPopupMenu("Color");
colorMenu.add(makeMenuItem("Red"));
colorMenu.add(makeMenuItem("Green"));
colorMenu.add(makeMenuItem("Blue"));

MouseListener mouseListener = new MouseAdapter( ) {
public void mousePressed(MouseEvent e) { checkPopup(e); }
public void mouseClicked(MouseEvent e) { checkPopup(e); }
public void mouseReleased(MouseEvent e) { checkPopup(e); }
private void checkPopup(MouseEvent e) {
if (e.isPopupTrigger( )) {
selectedComponent = e.getComponent( );
colorMenu.show(e.getComponent(), e.getX( ), e.getY( ));
}
}
};
frame.getContentPane( ).addMouseListener(mouseListener);

frame.setSize(200,50);
frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
frame.setVisible(true);
}
private JMenuItem makeMenuItem(String label) {
JMenuItem item = new JMenuItem(label);
return item;
}

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

Adding Border in Swing Application componenets

noreply@blogger.com (Unknown) — Thu, 08 Jul 2010 11:27:00 +0000

The Border class is in javax.swing.border package.Make sure you have imported the package before using borders in your application.You can add borders to components by using setBorder() method.This method has been declared in JComponent class and is available for all the components.Method getBorder() gives the name of border for the component.Borders add look and feel in your components.

BorderFactory class is used to create borders for a component.BorderFactory class has been declared in javax.swingpackage and contains method for creating various types of borders.

You can use following borders:-

Line Border
Etched Border
Bevel Border

Example for Line Border:-
import java.awt.*;
import javax.swing.*;
import javax.swing.border.*;
import javax.swing.BorderFactory.*;

public class bordertest extends JFrame{

public bordertest(){

JFrame frm=new JFrame("Border Test");
JButton button=new JButton("Line Border");
Border line=BorderFactory.createLineBorder(new Color(0,0,0),3);
button.setBorder(line);
frm.getContentPane().add(button);
frm.show();
frm.setSize(200,100);
}
public static void main(String a[]){
new bordertest();
}
}

createLineBorder() method is used to create a black line border that is three pixels wide.The setBorder() method is used to set the line border for the button.

Etched Border:-Replace the above code by following code from line 6.

/*
JButton button=new JButton("Etched Border");
Border etched=BorderFactory.createEtchedBorder();
button.setBorder(etched);
*/

createEtchedBorder() method is used to create Etched Border.

Bevel Border:-Bevel Border are of two types raised and lowered.You need to specify in the method createBevelBorder() which border you want.

Bevel Border Lowered:-Replace the line Border code by following code from line 6.

/*
JButton button=new JButton("Bevel Border");
Border bevellower=BorderFactory.createBevelBorder(BevelBorder.LOWERED);
button.setBorder(bevellower);
*/

Bevel Border Raised:-Replace the line Border code by following code from line 6.

/*
JButton button=new JButton("Bevel Border");
Border bevelraised=BorderFactory.createBevelBorder(BevelBorder.RAISED);
button.setBorder(bevelraised);
*/

Note:-Remove Comments from all the code before use.

Using Tabbed Panes in Java Swings

noreply@blogger.com (Unknown) — Thu, 08 Jul 2010 11:26:00 +0000

Tabbed panes are just like property sheets in windows environment.Using tabbed pane you can create multiple panels that are visible in a single area.A Tabbed pane consist of series of Tabs.These tabs are present on the basis of categories of information or application they contain.A tabbed pane enables you to display information in a small area in a more effective manner.The JTabbedPane class of javax.swing package is used to create Tabbed panes.Tabbed panes are effective way to use the window area.Tabbed Panes looks like following:-

Tabbed Pane source code:-

import javax.swing.*;
import java.awt.*;

public class Tabbedpane extends JFrame{
public static void main(String a[]){

//creating a container JFrame
JFrame frm=new JFrame("Tabbed Pane");

//Creating Tabbedpane
JTabbedPane jtpn=new JTabbedPane();
JPanel color=new JPanel();

//adding panel to a tabbed pane
jtpn.addTab("Color",null,color,"Color info");
color.add(new JLabel("The color is not set yet"));
JPanel sound=new JPanel();

//adding panel to a tabbed pane
jtpn.addTab("Sound",null,sound,"Sound info");
sound.add(new JLabel("The sound is off"));

//adding component to the container
frm.getContentPane().add(jtpn);
frm.setBounds(200,200,200,200);
frm.show();

}
}

JTabbedPane class is used to ceate JTabbedPane oblect.
For adding a JPanel to a JTabbedPane method named addTab() is used.
Four parameters of addTab() method are:-

1.Label for Tab.
2.Image(if any otherwise null).
3.Component to be added to the Tabbed pane.
4.ToolTip for the tab.

How to Set Icons on Swing Buttons

noreply@blogger.com (Unknown) — Thu, 08 Jul 2010 11:26:00 +0000

Swing Buttons provides many exclusive features that are not found in the Button class defined in the AWT package.Swing Buttons are the subclass of AbstractButton class,which extends JComponent.You can always associate an icon of your choice with a Swing Button.The Icons are set as program runs or set when some event is fired like button pressed.AbstractButton class contains many methods that allow you to control the behaviour of buttons,check boxes and Radio Buttons.There is the way you can set the icon on the swing button and it is through the JButton constructor.

Despite of being set by constructor we can change the Icon of our Button whenever some action is fired or some condition is met.We can define different Icons when button :-

1.is disabled
2.is pressed
3.is selected(for radio buttons etc)
4.gets mouse focus

JButton class is responsible for creation of all types of push buttons whether with icons or with text or both.The constructor used to create Button with Icon is

JButton(Icon i)

But if you also want to add Text with Icon then the constructor will be

JButton(String s ,Icon i)

In case you forgot to add text and you want to add text to the button whenever you want then use following method with JButton object.

setText(String str)

The following example will help in understanding how to set Icons and how you can change them according to your need.

import javax.swing.*;
import java.awt.event.*;
import javax.swing.AbstractButton;

public class ButtonImage extends JFrame implements ActionListener
{
JButton button;
public ButtonImage()
{
JFrame frm = new JFrame("Icon on Button");
JPanel panel = new JPanel();
ImageIcon imageicon = new ImageIcon("d:\\Anmtd_Feed.gif");
ImageIcon im = new ImageIcon("d:\\snap.jpg");
ImageIcon img = new ImageIcon("e:\\softwares\\ICON gallery\\Icons-1\\128 x 128\\apple1 (1).ico");
button = new JButton(imageicon);
button.setText("The Feed Icon");
panel.add(button);
button.addActionListener(this);
button.setDisabledIcon(im);
button.setRolloverIcon(img);
frm.getContentPane().add(panel);
frm.setVisible(true);
frm.setBounds(100,100,250,150);
}

public void actionPerformed(ActionEvent ae)
{
if (ae.getSource()==button)
{
button.setEnabled(false);
}
}

public static void main(String a[])
{
new ButtonImage();
}
}

This is first output Frame.In example it is shown that how we can change the button image when the button is disabled or whenever mouse moves over it.

The method setDisabledIcon(Icon i) and setRolloverIcon(Icon i) changes icons when the button is disabled or Hovered by Mouse respectively.ImageIcon is just a class which implements the Icon interface thus we are passing here ImageIcon as it is more convenient to use and most of all it implements Icon interface.

You can check on your own just change the Icon or Image paths then when the button is pressed the button is disabled and the image is changed once the button is disabled then there is no way you can change the icon of the button.That is why move mouse over the button first to test and then press the button.

How to use Swing Scroll Panes

noreply@blogger.com (Unknown) — Thu, 08 Jul 2010 11:25:00 +0000

A Scroll Pane is a component like JFrame or JPanel which is used to add other components but Scroll Pane has a Scroll Bar Associated with it which is a unique characteristic of this component Container.Scroll Panes are implemented in swing by JScrollPane class ,which extends JComponent class.Scroll Bar is either Vertical or Horizontal and they are used in Scroll Panes as needed.Like if you want to display the Scroll Bars all the time then you may use them always and also you might choose them to show up when container overflows.

Constructors used to create the Scroll Pane in Swings are :-

JScrollPane(Component cmp)
JScrollPane(int vert, int horiz)
JScrollPane(Component cmp, int vert, int horiz)

Remember:- A window can not be added to a Scroll Pane like JFrame cannot be added to a JScrollPane,but JPanel and other similar containers can be used which are not windows.

In above constructors cmp is the component to be added on the ScrollPane.vert and horiz are the integer constants that are defined when the horizontal or vertical ScrollBars are shown in the ScrollPane.These constants are defined in ScrollPaneConstants interface.

Some example constants are :-

1.VERTICAL_SCROLLBAR_ALWAYS (Always shows up vertical scrollbar) 2.VERTICAL_SCROLLBAR_AS_NEEDED(Shows up vertical Scrollbar when needed) 3.HORIZONTAL_SCROLLBAR_ALWAYS (Always shows up horizontal scrollbar)4.HORIZONTAL_SCROLLBAR_AS_NEEDED(Shows up horizontal Scrollbar when needed)

Lets take a look at following example which lets you learn how to create and use JScrollPanes in your applications.

import java.awt.*;
import javax.swing.*;

public class Scrollpanedemo extends JFrame
{
public Scrollpanedemo()
{
JFrame frm = new JFrame("Scroll Pane demo");
JPanel panel = new JPanel();
panel.setLayout(new GridLayout(20,5));
for(int i=0;i<100;i++)
{
panel.add(new JButton("Button no. " + (i+1)));
}
int v=ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED;
int h=ScrollPaneConstants.HORIZONTAL_SCROLLBAR_AS_NEEDED;
JScrollPane jsp = new JScrollPane(panel,v,h);
frm.getContentPane().add(jsp);
frm.setBounds(400,200,380,310);
frm.setVisible(true);
}

public static void main(String a[])
{
new Scrollpanedemo();
}
}

In the above example we create a frame and add a scrollpane over it.Then we create a panel which contains all the components and add it to the scrollpane.We have used the AS_NEEDED constants since we want to show that when our scrollpane overflows then the Scroll Bars shows up.

The " ? " Operator

noreply@blogger.com (Unknown) — Thu, 08 Jul 2010 11:24:00 +0000

Java includes a special Three-way(Ternary) operator that can replace certain types of if-then-else statements.These statements include assignment when certain conditions are fulfilled.This operator is " ? ".The working of " ? " operator is similar as in C,C++ and C#.The " ? " operator at first look might seem confusing but it is extremely useful in particular conditions when mastered.

General Syntax :-

expression 1 ? expression 2 : expression 3

Here expression 1 can be any expression that evaluates to a Boolean value.If expression 1 is true then expression 2 is evaluated else expression 3 is evaluated.Both the expressions expression 1 and expression 2 must have a return type,they can never be void.Make it more clear by understanding below example.

Example:-

public class optest
{
public static void main(String a[])
{
int ratio=0,num=20,denom=10;

/* The " ? " operator assignes 0 if condition denom==0 is true else it assigns num/denom to ratio if condituion is false*/

ratio=denom==0?0:num/denom;

System.out.println("The ratio is "+ratio);
}
}

Output:-
The ratio is 2

Explanation:-When Java evaluates this assignment expression ,it first looks at the expression to the left of the question mark.If denom equals to zero then expression 2 between ? and : is evaluated else last expression is evaluated.The resultant is then assigned to the ratio variable used in expression 1.

Java Game Aladdin

noreply@blogger.com (Unknown) — Thu, 08 Jul 2010 11:21:00 +0000

Have an adventure with Aladdin and his Princess Jasmin, with the helpof Genie.... Game based on the legendary Disney movie of the same name.

Download Java Game Aladdin