Showing the copyright symbol in a JLabel

Main.java:

import java.awt.event.*;
import javax.swing.*;
import java.awt.*;
   
public class Main extends JFrame {
   public Main() {
      getContentPane().setLayout(new FlowLayout());
 
      final JLabel label = new JLabel("Copyrightu00a9, All rights reserved");
      getContentPane().add(label);
 
      label.putClientProperty("html", null);
  
      addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent event) {
            System.exit(0);   
         }      
      });
 
      pack();
   }
 
   public static void main(String[] args) {
      (new Main()).show();
   }
}

Changing the color of one JTable cell

Main.java:

import javax.swing.table.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.*;
import java.awt.*;
 
public class Main extends JFrame {
   public Main() {
      super("TableModel Demonstration");
  
      // create our own custom TableModel
      WineTableModel wineModel = new WineTableModel();
      JTable table = new JTable(wineModel);
 
      // since we're using values of floats and boolean here, we need
      // to set the cell renderer for every column. 
      for (int i =0; i<wineModel.getColumnCount();i++) {
         table.setDefaultRenderer(table.getColumnClass(i), new WineCellRenderer());
      }
       
      // add rows to our TableModel, each row is represented as a Wine object
      wineModel.addWine(new Wine("Chateau Meyney, St. Estephe", "1994", 18.75f, true));
      wineModel.addWine(new Wine("Chateau Montrose, St. Estephe", "1975", 54.25f, true));
      wineModel.addWine(new Wine("Chateau Gloria, St. Julien", "1993", 22.99f, false));
      wineModel.addWine(new Wine("Chateau Beychevelle, St. Julien", "1970", 61.63f, false));
      wineModel.addWine(new Wine("Chateau La Tour de Mons, Margeaux", "1975", 57.03f, true));
      wineModel.addWine(new Wine("Chateau Brane-Cantenac, Margeaux", "1978", 49.92f, false));
 
      // create the scroll pane and add the table to it. 
      JScrollPane scrollPane = new JScrollPane(table);
 
      // add the scroll pane to this window.
      getContentPane().add(scrollPane, BorderLayout.CENTER);
 
      addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent e) {
            System.exit(0);
         }
      });
   }
 
   public static void main(String[] args) {
      Main main = new Main();
      main.pack();
      main.setVisible(true);
   }
}
 
// a simple object that holds data about a particular wine
class Wine {
   private String  name;
   private String  vintage;
   private float   price;
   private boolean inStock;
 
   public Wine(String name, String vintage, float price, boolean inStock) {
      this.name = name;
      this.vintage = vintage;
      this.price = price;
      this.inStock = inStock;
   }
 
   public String getName()     { return name; }
   public String getVintage()  { return vintage; }
   public float  getPrice()    { return price; } 
   public boolean getInStock() { return inStock; }
 
   public String toString() { 
      return "[" + name + ", " + vintage + ", " + price + ", " + inStock + "]"; }
}
 
class WineTableModel extends AbstractTableModel {
   // holds the strings to be displayed in the column headers of our table
   final String[] columnNames = {"Name", "Vintage", "Price", "In stock?"};
 
   // holds the data types for all our columns
   final Class[] columnClasses = {String.class, String.class, Float.class, Boolean.class};
 
   // holds our data
   final Vector data = new Vector();
  
   // adds a row
   public void addWine(Wine w) {
      data.addElement(w);
      fireTableRowsInserted(data.size()-1, data.size()-1);
   }
 
   public int getColumnCount() {
      return columnNames.length;
   }
         
   public int getRowCount() {
      return data.size();
   }
 
   public String getColumnName(int col) {
      return columnNames[col];
   }
 
   public Class getColumnClass(int c) {
      return columnClasses1;
   }
 
   public Object getValueAt(int row, int col) {
      Wine wine = (Wine) data.elementAt(row);
      if (col == 0)      return wine.getName();
      else if (col == 1) return wine.getVintage();
      else if (col == 2) return new Float(wine.getPrice());
      else if (col == 3) return new Boolean(wine.getInStock());
      else return null;
   }
 
   public Object getValueAtRow(int row) {
      Wine wine = (Wine) data.elementAt(row);
      return wine;
   }
 
   public boolean isCellEditable(int row, int col) {
      return false;
   }
}
 
class WineCellRenderer extends DefaultTableCellRenderer {
   public Component getTableCellRendererComponent(
            JTable table, Object value, boolean isSelected,
            boolean hasFocus, int row, int column)
   {
      WineTableModel wtm = (WineTableModel) table.getModel();
      Wine wine = (Wine) wtm.getValueAtRow(row);
 
      if (column == 3 && wine.getInStock() == false) {
         setBackground(Color.red);
      }
      else {
         setBackground(Color.white);
      }
 
      return super.getTableCellRendererComponent(table, value, isSelected, 
                                                 hasFocus, row, column);
   }
}

A Swing drag and drop code example

Drag and Drop is a powerful feature you should consider adding to your Java applications. When you check out the available tutorials on Java dnd, it may look fairly complex to you. Though it’s not all that hard, the hard part is remembering all the steps, objects and listeners involved. Here is a small example that shows you a basic drag and drop application (implemented with Swing).

A custom Drag and Drop (source) JList appears to the right and contains a file list of your root directory. Files with .txt extensions can be dragged upon our Drag and Drop JTextArea (target). The object transferred (Transferable) is a filename. When the drop occurs (you release the mouse button) the public void drop(DropTargetDropEvent event) is called. You can extract the filename from the Transferable object and go from there.

Main.java

import javax.swing.event.*;
import java.awt.event.*;
import javax.swing.*;
import java.awt.*;
import java.io.*;
 
public class Main extends JFrame
{
   private DNDJList list;
   private DNDJTextArea textarea;
 
   public static void main(String []args) {
      Main frame = new Main();
      frame.show();
   }
 
   public Main() {
      getContentPane().setLayout(new BorderLayout());
      list = new DNDJList(new DefaultListModel());
      getContentPane().add(BorderLayout.EAST, new JScrollPane(list));
      textarea = new DNDJTextArea();
      getContentPane().add(BorderLayout.CENTER, new JScrollPane(textarea));
 
      addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent e) {
            System.exit(0);
         }
      });
 
      fillUpList(&quot;c:\&quot;);
 
      setSize(700, 300);
   }

   /**
    *  Fills up the JList with the entries in the specified directory
    */
   private void fillUpList(String directory) {
      File dir = new File(directory);
      File []files = dir.listFiles();
 
      DefaultListModel dlm = (DefaultListModel) list.getModel();
      for (int i=0; i&lt;files.length; i++) {
         dlm.addElement(directory + files[i].getName());
      }
   }
}

Our drag and drop JTextArea: DNDJTextArea.java

import java.awt.*;
import java.awt.dnd.*;
import java.awt.datatransfer.*;

import java.io.*;
import java.io.IOException;
 
import javax.swing.JTextArea;
 
public class DNDJTextArea extends JTextArea implements DropTargetListener
{
   DropTarget dropTarget = null;
  
   public DNDJTextArea() {
      // create a drop target
      dropTarget = new DropTarget(this, this);
   }
 
   public void dragEnter(DropTargetDragEvent event) { 
      event.acceptDrag(DnDConstants.ACTION_MOVE);
   }
 
   public void drop (DropTargetDropEvent event) {
      try {
         // get the object that is being transferred
         Transferable transferable = event.getTransferable();
       
         // DNDJTextArea accepts only Strings
         if (transferable.isDataFlavorSupported(DataFlavor.stringFlavor)) {
            event.acceptDrop(DnDConstants.ACTION_MOVE);
 
            String filename = (String) transferable.getTransferData(DataFlavor.stringFlavor);
            setText(readFile(filename));

            event.getDropTargetContext().dropComplete(true);
         } 
         else {
            event.rejectDrop();
         }
      }
      catch (UnsupportedFlavorException e) {
         setText(&quot;&quot;+e);
         event.rejectDrop();
      }
      catch (Exception e) {
         setText(&quot;&quot;+e);
         event.rejectDrop();
      } 
   }
 
   public void dragExit (DropTargetEvent event) { }
   public void dragOver (DropTargetDragEvent event) { }
   public void dropActionChanged (DropTargetDragEvent event) { }
 
   public String readFile(String filename) throws Exception {
      String LINEEND = System.getProperties().getProperty(&quot;line.separator&quot;);      
      StringBuffer sb = new StringBuffer();
      BufferedReader br = new BufferedReader(new FileReader(filename));
 
      String line;
      while ((line = br.readLine()) != null) {
         sb.append(line + LINEEND);
      }         
 
      return sb.toString();
   }
}

A drag and drop JList:DNDJList.java

import java.awt.dnd.*;
import java.awt.datatransfer.*;
import java.io.IOException;
import java.io.*;
 
import javax.swing.*;
 
public class DNDJList extends JList implements DragSourceListener, DragGestureListener    
{
   DragSource dragSource = null;
 
   public DNDJList(ListModel lm) {
      super(lm);
 
      // create a dragsource
      dragSource = new DragSource();
 
      // create a drag gesture recognizer
      dragSource.createDefaultDragGestureRecognizer(this, DnDConstants.ACTION_MOVE, this);
   }    
 
   public void dragGestureRecognized( DragGestureEvent event) {  
      String fileSelected = (String) getSelectedValue();
 
      if (fileSelected != null) {
         if (fileSelected.endsWith(&quot;.txt&quot;)) {
            // StringSelection implements Transferable, wraps the data into a transferable object
            StringSelection text = new StringSelection(fileSelected.toString()); 
        
            // start the dragging
            dragSource.startDrag(event, DragSource.DefaultMoveDrop, text, this);
         }
         else {
            SwingUtilities.invokeLater(new Runnable() {
               public void run() {
                  JOptionPane.showMessageDialog(SwingUtilities.getRootPane(DNDJList.this), 
                                                &quot;Only .txt files can be dragged!&quot;, &quot;Error&quot;,
                                                JOptionPane.ERROR_MESSAGE);
               } 
            });
         }
      } else {
         System.out.println( &quot;nothing was selected&quot;);   
      }
   }
 
   public void dragDropEnd (DragSourceDropEvent event) { }
   public void dragEnter (DragSourceDragEvent event) { }
   public void dragExit (DragSourceEvent event) { }
   public void dragOver (DragSourceDragEvent event) { }
   public void dropActionChanged ( DragSourceDragEvent event) { }
}

Drawing a polygon in Swing

Create a Polygon object that contains all corners of the polygon and use the method drawPolygon to render it.

Main.java:

import java.awt.event.*;
import javax.swing.*;
import java.awt.*;
 
public class Main extends JFrame {
   public Main() {
      addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent we) {
            System.exit(1);
         }
      });
   }
 
   public void paint(Graphics g) {
      Graphics2D g2d = (Graphics2D) g;
 
      Polygon p = new Polygon();
      p.addPoint(110, 120);
      p.addPoint(120, 110);
      p.addPoint(130, 110);
      p.addPoint(140, 120);
      p.addPoint(140, 130);
      p.addPoint(130, 140);
      p.addPoint(120, 140);
      p.addPoint(110, 130);
      p.addPoint(110, 120);
 
      g2d.drawPolygon(p);
   }
 
   public static void main(String []args) {
      Main main = new Main();
      main.setSize(300, 300);
      main.setVisible(true);
   }
}

Getting the dimensions of a text in Swing

This example shows you how to center a text on the JFrame. It will take into account the specifics of the chosen font. Run it from command line like java Main Helvetica.

Main.java:

import java.awt.image.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.*;
import java.awt.*;
 
public class Main extends JFrame {
   private String fontname;
   private String text = "Easter Island";
 
   public Main(String fontname) {
      this.fontname = fontname;
 
      addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent we) {
            System.exit(1);
         }
      });
   } 

   public void paint(Graphics g) {
      super.paint(g);
 
      Graphics2D g2d = (Graphics2D) g;
      Font f = new Font(fontname, Font.BOLD, 36);
      FontMetrics fm = getFontMetrics(f);
 
      int swidth = fm.stringWidth(text);
      int sheight = fm.getAscent();
 
      int width = getSize().width;
      int height = getSize().height;
 
      g2d.setColor(Color.gray);
      g2d.drawLine(0, height/2, width, height/2);
      g2d.drawLine(width/2, 0, width/2, height);
 
      g2d.setColor(Color.black);
      g2d.setFont(f);
      g2d.drawString(text, width/2 - swidth/2, height/2 + sheight/2);
   }
  
   public static void main(String []args) {
      if (args.length == 0) {
         System.err.println("Usage: java Main <fontname>");
         System.exit(1);
      }
 
      Main main = new Main(args[0]);
      main.setVisible(true);
      main.setSize(300, 300);
   }
}

Drawing a textured rectangle in Swing

Main.java:

import java.awt.image.*;
import java.awt.event.*;
import java.awt.geom.*;
import javax.swing.*;
import java.awt.*;
 
public class Main extends JFrame {
   private BufferedImage image; 
 
   public Main() {
      addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent we) {
            System.exit(1);
         }
      });
 
      image = toBufferedImage(new javax.swing.ImageIcon("c:\djkrush.jpg").getImage());
   }
 
   public void paint(Graphics g) {
      Graphics2D g2d = (Graphics2D) g;
 
      Rectangle2D tr = new Rectangle2D.Double(0, 0, image.getWidth(), image.getHeight());
      TexturePaint tp = new TexturePaint(image, tr);
 
      // draw texture filled ellipse, but with antialiasing
      g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                           RenderingHints.VALUE_ANTIALIAS_ON);
      BasicStroke bs = new BasicStroke(5, BasicStroke.CAP_BUTT, BasicStroke.JOIN_MITER,
                           10, null, 0);
      g2d.setStroke(bs);
      g2d.setPaint(tp);
      g2d.drawRect(10, 40, 150, 150);
   }
 
   public BufferedImage toBufferedImage(Image image) {
      BufferedImage bi = new BufferedImage(image.getWidth(null), image.getHeight(null), 
                                           BufferedImage.TYPE_INT_RGB); 
 
      // copy the original image
      Graphics g = bi.createGraphics();
    
      g.drawImage(image, 0, 0, null);
      g.dispose();
 
      return bi;
   }
 
   public static void main(String []args) {
      Main main = new Main();
      main.setSize(170, 210);
      main.setVisible(true);
   }
}

Image used:

Inverting an image

To invert an image, you can use the class LookupOp. This class works with one or more tables that will be applied to the color values of the pixels. To invert an RGB image, every R, G, and B value are subtracted from 256. The lookup table reflects these changes.

The following example shows the original image and an image that has been inverted.

Main.java:

import java.awt.image.*;
import java.awt.event.*;
import javax.swing.*;
import java.awt.*;
 
public class Main extends JFrame {
   private boolean firstTime = true;
   private BufferedImage sourceBi;
   private BufferedImage destBi;
 
   public Main() {
      addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent we) {
            System.exit(1);
         }
      }); 
   } 
 
   public void paint(Graphics graphics) {
      Graphics2D g2d = (Graphics2D) graphics;
  
      if (firstTime) {
         Image img = new javax.swing.ImageIcon("meatballs.jpg").getImage(); 
         sourceBi = toBufferedImage(img);
         destBi = new BufferedImage(sourceBi.getWidth(), sourceBi.getHeight(), 
                                    BufferedImage.TYPE_INT_RGB);
         setSize(sourceBi.getWidth(), sourceBi.getHeight()*2);
 
         byte[] intensity = new byte[256];
         for(int i=0; i<256; i++) {
            intensity[i] = (byte) (256 - i);
         }
  
         ByteLookupTable blt = new ByteLookupTable(0, intensity);
         LookupOp op = new LookupOp(blt, null);
         destBi = op.filter(sourceBi, null);
 
         firstTime = false;
      }
 
      g2d.drawImage(sourceBi, 0, 0, this);
      g2d.drawImage(destBi, 0, sourceBi.getHeight(), this);
   }
 
   public static BufferedImage toBufferedImage(Image image) {
      BufferedImage bi = new BufferedImage(image.getWidth(null), image.getHeight(null), 
                                           BufferedImage.TYPE_INT_RGB); 
 
      // copy the original image
      Graphics g = bi.createGraphics();
    
      g.drawImage(image, 0, 0, null);
      g.dispose();
 
      return bi;
   }
 
   public static void main(String []args) {
      Main main = new Main();
      main.setVisible(true);
      main.setSize(300, 150);
   }
}

Image used:

To learn more about image processing,
check out this expensive but excellent book:

Detecting if the right button was clicked in Swing

To determine whether a right mouse click button was clicked or not, write code in the mouseClicked function of the mouseListener Interface.

   class MyMouseListener extends MouseAdapter
   {
      public void mouseClicked(MouseEvent me)
      {
         if ((me.getModifiers() & InputEvent.BUTTON3_MASK) != 0)
            // right mouse clicked......   
         }
      }
   };
 
   /* getModifiers() gives constant modifier for a particular click();
      BUTTON3_MASK is constant modifier for the right moouse click */

Examples of Swing borders

You can combine these borders with CompoundBorder.

Main.java:

import javax.swing.border.*;
import java.awt.event.*;
import javax.swing.*;
import java.awt.*;
 
public class Main extends JFrame
{
   public Main() {
      getContentPane().setLayout(new FlowLayout(FlowLayout.LEFT));
 
      JLabel labels[] = new JLabel[6];
      labels[0] = new JLabel("Label with EmptyBorder, margin 20");
      labels[0].setBorder(new EmptyBorder(20, 20, 20, 20));
      labels[1] = new JLabel("Label with LineBorder, red color, thickness 3");
      labels[1].setBorder(new LineBorder(Color.red, 3));
      labels[2] = new JLabel("Label with LOWERED BevelBorder");
      labels[2].setBorder(new BevelBorder(BevelBorder.LOWERED));
      labels[3] = new JLabel("Label with RAISED EtchedBorder");
      labels[3].setBorder(new EtchedBorder(EtchedBorder.RAISED));
      labels[4] = new JLabel("Label with MatteBorder and Icon");
      labels[4].setBorder(new MatteBorder(new ImageIcon("c:\female.gif")));
      labels[5] = new JLabel("Label with BevelBorder TitledBorder");
      labels[5].setBorder(new TitledBorder(new BevelBorder(BevelBorder.LOWERED), "Title"));
 
      for (int i=0; i<labels.length; i++) {
         labels[i].setOpaque(true);
         getContentPane().add(labels[i]);
      }
      
      addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent we) {
            System.exit(0);
         }
      });
   }
 
   public static void main(String [] args) {
      Main main = new Main();
      main.setSize(300, 400);
      main.setVisible(true);
   } 
} 

Maximizing a JFrame

This is as close as you can get: just resize the window to the current screensize:

 
import javax.swing.*;
import java.awt.*;
   
public class Maximize extends JFrame {
 
   public Maximize() {
      Toolkit tk = getToolkit();
      
      setSize((int) getToolkit().getScreenSize().getWidth(), 
              (int) getToolkit().getScreenSize().getHeight());
   }
 
   public static void main(String args[]) {
      new Maximize().setVisible(true);     
   }
}