Detecting a cell selection in a JTable

You can do so with a combination of a ColumnModelListener and a TableSelectionListener. An easier way is to register a MouseListener to your JTable as shown in following example.

Main.java:

import javax.swing.table.*;
import javax.swing.event.*;
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();
      final JTable table = new JTable(wineModel);
 
      // 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);
 
      table.addMouseListener(new MouseAdapter() {
         public void mouseClicked(MouseEvent e) { 
            if (e.getClickCount() >= 1) {
               int row = table.getSelectedRow();
               int col = table.getSelectedColumn();
 
               if (row == -1 || col == -1) return;
               System.out.println("cell [" + row +","+ col +"]");
            }
         }
      });
 
      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 boolean isCellEditable(int row, int col) {
      return false;
   }
}

Creating a JTable with images in the headers

Courtesy of Nobuo Tamemasa (http://www2.gol.com/users/tame/swing/examples/JTableExamples8.html)



AnimatedIconHeaderExample.java:

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

/**
 * @version 1.0 06/19/99
 */
public class AnimatedIconHeaderExample extends JFrame {

  public AnimatedIconHeaderExample(){
    super( "AnimatedIconHeader Example" );
    
    final Object[][] data =  new Object[][]{
      {"Leopard","Lycaon"},
      {"Jagur"  ,"Jackal"},
      {"Cheetah","Coyote"},
      {"Puma"   ,"Dingo" },
      {"Lynx"   ,"Fox"   },
      {"Tom"    ,"Hot"  }};
    final String[] column = new String[]{"Cat","Dog"};
    
    ImageIcon[] icons = {new ImageIcon("images/3-119.gif"),
                         new ImageIcon("images/3-6.gif")};
        
    AbstractTableModel model = new AbstractTableModel() {
      public int getColumnCount() { return column.length; }
      public int getRowCount()    { return data.length; }
      public String getColumnName(int col) {
       return column[col]; 
      }
      public Object getValueAt(int row, int col) { 
        return data[row][col]; 
      }
    };
        
    JTable table = new JTable( model );
    JTableHeader header = table.getTableHeader();
    JLabel renderer;
    for (int i=0;i<model.getColumnCount();i++) {
      renderer = (JLabel)table.getColumn(column[i]).getHeaderRenderer();
      renderer.setIcon(icons[i]);
      
      // If you have only one column.
      // icons[i].setImageObserver(header);
      
      icons[i].setImageObserver(new HeaderImageObserver(header, i));
    }
    JScrollPane pane = new JScrollPane(table);
    getContentPane().add(pane);
  }
    
  class HeaderImageObserver implements ImageObserver {
    JTableHeader header;
    int col;
      
    HeaderImageObserver(JTableHeader header, int col) {
      this.header = header;
      this.col    = col;
    }
    
    public boolean imageUpdate(Image img, int flags,
                               int x, int y, int w, int h) {
      if ((flags & (FRAMEBITS|ALLBITS)) != 0) {
        Rectangle rect = header.getHeaderRect(col);
        header.repaint(rect);
      }
      return (flags & (ALLBITS|ABORT)) == 0;
    }
  }    
  
  public static void main(String[] args) {
    AnimatedIconHeaderExample frame = new AnimatedIconHeaderExample();
    frame.addWindowListener(new WindowAdapter() {
      public void windowClosing(WindowEvent e) {
        System.exit(0);
      }
    });
    frame.setSize( 300, 140 );
    frame.setVisible(true);
  }
}

Creating borders for JTable columns

Courtesy of Nobuo Tamemasa (http://www2.gol.com/users/tame/swing/examples/JTableExamples7.html)



ColumnBorderTableExample.java:

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.table.*;
import javax.swing.event.*;
 
/**
 * @version 1.0  3/06/99
 */
public class ColumnBorderTableExample extends JFrame {

  public ColumnBorderTableExample() {
    super( "Column Border Example" );
        
    DefaultTableModel dm = new DefaultTableModel(4,10);
    JTable table = new JTable( dm );
    table.setIntercellSpacing(new Dimension(0,0));
    
    Color color = table.getGridColor();
    BorderCellRenderer[] renderers = new BorderCellRenderer[6];
    renderers[0] = createRenderer(color, new Insets(0,0,0,1));
    renderers[1] = createRenderer(color, new Insets(0,1,0,1));
    renderers[2] = createRenderer(color, new Insets(0,1,0,2));
    renderers[3] = createRenderer(color, new Insets(0,2,0,2));
    renderers[4] = createRenderer(color, new Insets(0,2,0,0));
    renderers[5] = createRenderer(Color.red, new Insets(0,1,1,1));
    
    TableColumnModel model = table.getColumnModel();
    model.getColumn(1).setCellRenderer(renderers[0]);
    model.getColumn(2).setCellRenderer(renderers[0]);
    model.getColumn(3).setCellRenderer(renderers[0]);
    model.getColumn(4).setCellRenderer(renderers[1]);
    model.getColumn(5).setCellRenderer(renderers[2]);
    model.getColumn(6).setCellRenderer(renderers[3]);
    model.getColumn(7).setCellRenderer(renderers[4]);
    model.getColumn(8).setCellRenderer(renderers[5]);
    
    JScrollPane scroll = new JScrollPane( table );
    getContentPane().add(scroll, BorderLayout.CENTER);
  }

  public static void main(String[] args) {
    ColumnBorderTableExample frame = new ColumnBorderTableExample();
    frame.addWindowListener( new WindowAdapter() {
      public void windowClosing( WindowEvent e ) {
        System.exit(0);
      }
    });
    frame.setSize( 300, 120 );
    frame.setVisible(true);
  }
  
  private static BorderCellRenderer createRenderer(Color color, Insets insets) {
    BorderCellRenderer renderer = new BorderCellRenderer();
    renderer.setColumnBorder(new LinesBorder(color, insets));    
    return renderer;
  }  
}

BorderCellRenderer.java:

import java.awt.*;
import javax.swing.*;
import javax.swing.table.*;
import javax.swing.border.*;
 
/**
 * @version 1.0 03/06/99
 */
public class BorderCellRenderer extends JLabel
    implements TableCellRenderer {
  protected Border noFocusBorder; 
  protected Border columnBorder; 
 
  public BorderCellRenderer() {
    noFocusBorder = new EmptyBorder(1, 2, 1, 2);
    setOpaque(true);
  }

  public Component getTableCellRendererComponent(JTable table, Object value,
                 boolean isSelected, boolean hasFocus, int row, int column) {
    if (isSelected) {
      setForeground(table.getSelectionForeground());
      setBackground(table.getSelectionBackground());
    } else {
      setForeground(table.getForeground());
      setBackground(table.getBackground());
    }
    setFont(table.getFont());
    
    if (hasFocus) {
      setBorder( UIManager.getBorder("Table.focusCellHighlightBorder") );
      if (table.isCellEditable(row, column)) {
        setForeground( UIManager.getColor("Table.focusCellForeground") );
        setBackground( UIManager.getColor("Table.focusCellBackground") );
      }
    } else {
      if (value instanceof CellBorder) {
        Border border = ((CellBorder)value).getBorder();
        setBorder(border);
      } else {
        if (columnBorder != null) {
          setBorder(columnBorder);
        } else {
          setBorder(noFocusBorder);
        }
      }
    }
    setText((value == null) ? "" : value.toString());        
    return this;
  }
  
  public void setColumnBorder(Border border) {
    columnBorder = border;
  }
  
  public Border getColumnBorder() {
    return columnBorder;
  }
}

CellBorder.java:

import java.awt.*;
import javax.swing.border.*;
 
/**
 * @version 1.0 03/06/99
 */
public interface CellBorder {
   
  public Border getBorder();
  public Border getBorder(int row, int column);
  
  public void setBorder(Border border);
  public void setBorder(Border border, int row, int column);
}

LinesBorder.java:

import java.awt.*;
import javax.swing.*;
import javax.swing.border.*;
 
/**
 * @version 1.0 03/09/99
 */
public class LinesBorder extends AbstractBorder implements SwingConstants { 
  protected int northThickness;
  protected int southThickness;
  protected int eastThickness;
  protected int westThickness;  
  protected Color northColor;
  protected Color southColor;
  protected Color eastColor;
  protected Color westColor;
  
  public LinesBorder(Color color) {
    this(color, 1);
  }

  public LinesBorder(Color color, int thickness)  {
    setColor(color);
    setThickness(thickness);
  }

  public LinesBorder(Color color, Insets insets)  {
    setColor(color);
    setThickness(insets);
  }

  public void paintBorder(Component c, Graphics g, int x, int y, int width, int height) {
    Color oldColor = g.getColor();
    
    g.setColor(northColor);
    for (int i = 0; i < northThickness; i++)  {
      g.drawLine(x, y+i, x+width-1, y+i);
    }
    g.setColor(southColor);
    for (int i = 0; i < southThickness; i++)  {
      g.drawLine(x, y+height-i-1, x+width-1, y+height-i-1);
    }
    g.setColor(eastColor);
    for (int i = 0; i < westThickness; i++)  {
      g.drawLine(x+i, y, x+i, y+height-1);
    }
    g.setColor(westColor);
    for (int i = 0; i < eastThickness; i++)  {
      g.drawLine(x+width-i-1, y, x+width-i-1, y+height-1);
    }

    g.setColor(oldColor);
  }

  public Insets getBorderInsets(Component c)       {
    return new Insets(northThickness, westThickness, southThickness, eastThickness);
  }

  public Insets getBorderInsets(Component c, Insets insets) {
    return new Insets(northThickness, westThickness, southThickness, eastThickness);    
  }


  public boolean isBorderOpaque() { return true; }
    
  public void setColor(Color c) {
    northColor = c;
    southColor = c;
    eastColor  = c;
    westColor  = c;
  }
  
  public void setColor(Color c, int direction) {
    switch (direction) {
      case NORTH: northColor = c; break;
      case SOUTH: southColor = c; break;
      case EAST:  eastColor  = c; break;
      case WEST:  westColor  = c; break;
      default: 
    }
  }
    
  public void setThickness(int n) {
    northThickness = n;
    southThickness = n;
    eastThickness  = n;
    westThickness  = n;
  }
    
  public void setThickness(Insets insets) {
    northThickness = insets.top;
    southThickness = insets.bottom;
    eastThickness  = insets.right;
    westThickness  = insets.left;
  }
  
  public void setThickness(int n, int direction) {
    switch (direction) {
      case NORTH: northThickness = n; break;
      case SOUTH: southThickness = n; break;
      case EAST:  eastThickness  = n; break;
      case WEST:  westThickness  = n; break;
      default: 
    }
  }

  public void append(LinesBorder b, boolean isReplace) {
    if (isReplace) {
      northThickness = b.northThickness;
      southThickness = b.southThickness;
      eastThickness  = b.eastThickness;
      westThickness  = b.westThickness;
    } else {
      northThickness = Math.max(northThickness ,b.northThickness);
      southThickness = Math.max(southThickness ,b.southThickness);
      eastThickness  = Math.max(eastThickness  ,b.eastThickness);
      westThickness  = Math.max(westThickness  ,b.westThickness);
    }
  }

  public void append(Insets insets, boolean isReplace) {
    if (isReplace) {
      northThickness = insets.top;
      southThickness = insets.bottom;
      eastThickness  = insets.right;
      westThickness  = insets.left;
    } else {
      northThickness = Math.max(northThickness ,insets.top);
      southThickness = Math.max(southThickness ,insets.bottom);
      eastThickness  = Math.max(eastThickness  ,insets.right);
      westThickness  = Math.max(westThickness  ,insets.left);
    }
  }
}

Opening a new window when double clicking on a JTable row

Add a MouseListener to your JTable.

Main.java:

import java.awt.event.*;
import javax.swing.*;
import java.awt.*;
 
public class Main extends JFrame 
{
   public Main() {
      super("Table example, Wines from Bordeaux");
 
      final Object[][] tabledata = {
            { "Chateau Meyney, St. Estephe", 	   new Integer(1994), "$18.75"},
            { "Chateau Montrose, St. Estephe", 	   new Integer(1975), "$54.25" },
            { "Chateau Gloria, St. Julien", 	   new Integer(1993), "$22.99" },
            { "Chateau Beychevelle, St. Julien",   new Integer(1970), "$61.63" },
            { "Chateau La Tour de Mons, Margeaux", new Integer(1975), "$57.03" },
            { "Chateau Brane-Cantenac, Margeaux",  new Integer(1978), "$49.92" },
      };
 
      String columnheaders[] = { "Wine", "Vintage", "Price" };
 
      JTable table = new JTable(tabledata, columnheaders) {
         public boolean editCellAt(int row, int column, java.util.EventObject e) {
            return false;
         }
      };
 
      table.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
      table.setPreferredScrollableViewportSize(new Dimension(500, 70));
      JScrollPane scrollPane = new JScrollPane(table);
      getContentPane().add(scrollPane);
 
      addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent we) {
            System.exit(0);
         }
      });
 
      pack();
 
      table.addMouseListener(new MouseAdapter() {
         public void mouseClicked(MouseEvent e) {
            if (e.getClickCount() == 2) {
               JTable target = (JTable) e.getSource();
               int row = target.getSelectedRow();
               StringBuffer sb = new StringBuffer();
               String lineSeparator = System.getProperty("line.separator");
               sb.append(tabledata[row][0] + lineSeparator);
               sb.append(tabledata[row][1] + lineSeparator);
               sb.append(tabledata[row][2] + lineSeparator);
               TextFrame textFrame = new TextFrame(sb.toString());
               textFrame.setVisible(true);
            }
         }
      });
   }
 
   public static void main(String []args) {
      Main main = new Main();
      main.show();
   }
}
 
class TextFrame extends JFrame
{
   public TextFrame(String content) {
      super("TextFrame");
 
      JTextArea ta = new JTextArea();
      ta.setText(content);
      getContentPane().add(ta);
      addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent we) {
            dispose();
         }
      });
      
      setSize(200, 100);
   }
}

Render HTML documents

JEditorPane is able to display and edit different kinds of content. By default,
text/plain, text/html and text/rtf are recognized and passed on to the
EditorKit that is designed to handle it: DefaultEditorKit, HTMLEditorKit and
RTFEditorKit
. In the following example, a URL can be given in a JTextField.
Clicking GO will invoke the setPage method on the JEditorPane that will load
the page into a default document and set the content type. Using the
mime type of the page, the pane will automatically detect the correct EditorPane to
use.
Try: http://www.yahoo.com and http://www.esus.com/richtext.rtf

import javax.swing.text.html.*;
import javax.swing.text.*;
import java.awt.event.*;
import javax.swing.*;
import java.net.*;
import java.awt.*;
import java.io.*;
 
public class Main extends JFrame
{
   public static void main(String []args) {
      Main main = new Main();
      main.show();
   }
 
   public Main() {
 
      JButton uriButton = new JButton("Go!");
      // needs to be final to allow the inner class to access it!
      final JTextField uriTextField = new JTextField();
      final JEditorPane htmlPane = new JEditorPane();
      uriTextField.setText("http://www.yahoo.com");
      htmlPane.setEditable(false);
 
      uriButton.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent ae) {
            try {
               htmlPane.setPage(new URL(uriTextField.getText()));
            }
            catch(Exception e) {
               System.out.println(e);
            }
         }
      });
 
      getContentPane().setLayout(new BorderLayout());
      JPanel topPanel = new JPanel(new BorderLayout());
      topPanel.add(BorderLayout.CENTER, uriTextField);
      topPanel.add(BorderLayout.EAST, uriButton);
 
      getContentPane().add(BorderLayout.NORTH, topPanel);
      getContentPane().add(BorderLayout.CENTER, new JScrollPane(htmlPane));
 
      addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent e) {
            System.exit(0);
         }
      });
 
      setSize(400, 400);
   }
}

Preventing a JTree to be expanded or collapsed

Use the TreeWillExpandListener interface!

The following example allows expanding of nodes, but prevents collapsing.

Main.java:

import javax.swing.*;
import javax.swing.tree.*;
import javax.swing.event.*;
import java.awt.*;
import java.net.*;
import java.awt.event.*;
 
public class Main extends JFrame
{
   public Main() {
      DefaultMutableTreeNode root = createNodes();
      JTree tree = new JTree(root);
 
      tree.addTreeWillExpandListener(new TreeWillExpandListener() {
         public void treeWillCollapse(TreeExpansionEvent event) 
                            throws ExpandVetoException 
         {
            // prevent collapsing
            throw new ExpandVetoException(event);
 
         }
         public void treeWillExpand(TreeExpansionEvent event) 
                            throws ExpandVetoException 
         {
            // do nothing
         }
      });
 
      getContentPane().add(new JScrollPane(tree));
 
      addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent we) {
            System.exit(0);
         }
      });
   }
 
   public static DefaultMutableTreeNode createNodes() {
      DefaultMutableTreeNode root = new DefaultMutableTreeNode("Java");
      
      DefaultMutableTreeNode j2se = new DefaultMutableTreeNode("J2SE");
      DefaultMutableTreeNode j2ee = new DefaultMutableTreeNode("J2EE");
      DefaultMutableTreeNode j2me = new DefaultMutableTreeNode("J2ME");
 
      j2se.add(new DefaultMutableTreeNode("http://java.sun.com/j2se/"));
      j2ee.add(new DefaultMutableTreeNode("http://java.sun.com/j2ee/"));
      j2me.add(new DefaultMutableTreeNode("http://java.sun.com/j2me/"));
 
      root.add(j2se);
      root.add(j2ee);
      root.add(j2me);
 
      return root;
   }
 
   public static void main(String []args) {
      Main main = new Main();
      main.setSize(400, 400);
      main.setVisible(true);
   }
}

Aligning the drop-down arrow of a JComboBox to the right

Main.java:

import java.awt.event.*;
import javax.swing.*;
import java.awt.*;
 
public class Main extends JFrame
{
   public Main() {
      this.addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent we) {
            System.exit(0);
         }
      });
 
      getContentPane().setLayout(new FlowLayout(FlowLayout.LEFT));
      Object []items = new Object[] { "one", "two", "three", "four", 
                                      "five", "six", "seven" };
      JComboBox comboBox = new JComboBox(items);
      getContentPane().add(comboBox);
      comboBox.setComponentOrientation(ComponentOrientation.RIGHT_TO_LEFT);
   }
 
   public static void main(String []args) {
      Main main = new Main();
      main.setSize(200, 200);
      main.setVisible(true);
   }
}

Creating a JList with icons and text

Main.java:

import java.awt.image.*;
import javax.swing.*;
import java.util.*;
import java.awt.*;
  
public class Main 
{
   public static void main(String args[]) {
      JFrame frame = new JFrame("JList ImageIcon Demonstration");
 
      DefaultListModel dlm = new DefaultListModel();
      dlm.addElement(new ListEntry("Audio", new ImageIcon("audio.gif")));
      dlm.addElement(new ListEntry("Control Panel", new ImageIcon("controlpanel.gif")));
      dlm.addElement(new ListEntry("Folder", new ImageIcon("folder.gif")));
      dlm.addElement(new ListEntry("Local Disk (C:)", new ImageIcon("mycomp.gif")));
      dlm.addElement(new ListEntry("doc on '192.168.0.1' (Z:)", new ImageIcon("network.gif")));
 
      JList list = new JList(dlm);
      list.setCellRenderer(new ListEntryCellRenderer());
         
      frame.getContentPane().add(BorderLayout.CENTER, new JScrollPane(list)); 
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.pack();
      frame.setVisible(true);
   }
}
 
class ListEntry 
{
   private String value;
   private ImageIcon icon;
 
   public ListEntry(String value, ImageIcon icon) {
      this.value = value;
      this.icon = icon;
   }
 
   public String getValue() {
      return value;
   }
 
   public ImageIcon getIcon() {
      return icon;
   }
 
   public String toString() {
      return value;
   }
}
 
class ListEntryCellRenderer
 extends JLabel implements ListCellRenderer
{
   private JLabel label;
 
   public Component getListCellRendererComponent(JList list, Object value,
                                                 int index, boolean isSelected,
                                                 boolean cellHasFocus) {
      ListEntry entry = (ListEntry) value;
 
      setText(value.toString());
      setIcon(entry.getIcon());
  
      if (isSelected) {
         setBackground(list.getSelectionBackground());
         setForeground(list.getSelectionForeground());
      }
      else {
         setBackground(list.getBackground());
         setForeground(list.getForeground());
      } 
 
      setEnabled(list.isEnabled());
      setFont(list.getFont());
      setOpaque(true);
 
      return this;
   }
}

Maximizing an AWT Frame

From 1.3 onwards, use setExtendedState(Frame.MAXIMIZED_BOTH)

Main.java:

import java.awt.event.*;
import java.awt.*;
 
public class Main extends Frame implements ActionListener
{
   public Main()
   {
      addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent we) {
            System.exit(1);
         }
      });
 
      Button maxButton = new Button("Maximize this Frame");
      setLayout(new FlowLayout(FlowLayout.LEFT));
      add(maxButton);
      maxButton.addActionListener(this);
   }
 
   public void actionPerformed(ActionEvent ae) {     
      setExtendedState(Frame.MAXIMIZED_BOTH);
   }
 
   public static void main(String args[])
   {
      Main main = new Main();
      main.setSize(300, 150);
      main.setVisible(true);
   }
}

Drawing a filled round rectangle in Swing

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;
  
      g2d.setColor(Color.green);
      g2d.fillRoundRect(10, 50, 150, 70, 50, 30);
   }
 
   public static void main(String []args) {
      Main main = new Main();
      main.setSize(170, 150);
      main.setVisible(true);
   }
}