Creating an always-on-top SWT Shell

Use the style SWT.ON_TOP when you create the Shell.

Main.java:

import org.eclipse.swt.SWT;
import org.eclipse.swt.events.SelectionAdapter;
import org.eclipse.swt.events.SelectionEvent;
import org.eclipse.swt.events.SelectionListener;
import org.eclipse.swt.graphics.Color;
import org.eclipse.swt.layout.GridData;
import org.eclipse.swt.layout.GridLayout;
import org.eclipse.swt.widgets.Button;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Event;
import org.eclipse.swt.widgets.Group;
import org.eclipse.swt.widgets.Listener;
import org.eclipse.swt.widgets.Shell;
 
public class Main { 
   static Display display;
   static Shell shell;
   static Color color;
    
   public static void main(String[] args) {
      display = new Display();
      shell = new Shell(display);
 
      // pos x, pos y, width, height
      shell.setBounds(200, 200, 400, 200);
      shell.setText("SWT Shell Demonstration");
      shell.setLayout(new GridLayout());
 
      final Group buttonGroup = new Group(shell, SWT.NONE);
      GridLayout gridLayout = new GridLayout();
      gridLayout.numColumns = 3;
      buttonGroup.setLayout(gridLayout);
      buttonGroup.setLayoutData(new GridData(GridData.FILL_HORIZONTAL));
       
      final Button createShellButton = new Button(buttonGroup, SWT.PUSH);
      createShellButton.setText("Open Shell");
 
      SelectionListener selectionListener = new SelectionAdapter () {
         public void widgetSelected(SelectionEvent event) {
            final Shell childShell = new Shell(SWT.RESIZE | SWT.CLOSE | SWT.ON_TOP);
            Button closeButton = new Button(childShell, SWT.PUSH);
            closeButton.setBounds(10, 10, 100, 30);
            closeButton.setText("Close Shell");
            closeButton.addListener(SWT.Selection, new Listener() {
               public void handleEvent(Event event) {
                  childShell.dispose();
               }
            });
          
            childShell.setSize (300, 100);
            childShell.setText ("Title of Shell");
            childShell.open ();                  
         };
      };
       
      createShellButton.addSelectionListener(selectionListener);
       
      shell.open();
 
      while (!shell.isDisposed()) {
         if (!display.readAndDispatch()) {
            display.sleep();
         }
      }
      if (color != null && !color.isDisposed()) {
         color.dispose();
      }
      display.dispose();
   }
}

Setting the alignment on a Label in SWT

Main.java:

import org.eclipse.swt.SWT;
import org.eclipse.swt.events.SelectionAdapter;
import org.eclipse.swt.events.SelectionEvent;
import org.eclipse.swt.events.SelectionListener;
import org.eclipse.swt.layout.GridData;
import org.eclipse.swt.layout.GridLayout;
import org.eclipse.swt.widgets.Button;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Group;
import org.eclipse.swt.widgets.Label;
import org.eclipse.swt.widgets.Shell;
 
public class Main {
   public static void main(String[] args) {
      Display display = new Display();
      Shell shell = new Shell(display);
 
      // pos x, pos y, width, height
      shell.setBounds(200, 200, 300, 200);
      shell.setText("Label Demonstration");
      shell.setLayout(new GridLayout());
             
      final Label label = new Label(shell, SWT.BORDER | SWT.WRAP);
      label.setLayoutData(new GridData(GridData.FILL_HORIZONTAL | GridData.FILL_VERTICAL));
      label.setText("`I quite agree with you,' said the Duchess; `and the moral " +
                    "of that is--Be what you would seem to be--or if you'd like " +
                    "it put more simply--Never imagine yourself not to be " +
                    "otherwise than what it might appear to others that what " +
                    "you were or might have been was not otherwise than what " +
                    "you had been would have appeared to them to be otherwise.'");
       
      Group buttonGroup = new Group(shell, SWT.NONE);
      GridLayout gridLayout = new GridLayout();
      gridLayout.numColumns = 1;
      buttonGroup.setLayout(gridLayout);
      buttonGroup.setLayoutData(new GridData(GridData.FILL_VERTICAL));
       
      SelectionListener selectionListener = new SelectionAdapter () {
         public void widgetSelected(SelectionEvent event) {
            Button button = ((Button) event.widget);
            if (button.getText().equals("Left")) {
               label.setAlignment(SWT.LEFT);
            }
            else if (button.getText().equals("Right")) {
               label.setAlignment(SWT.RIGHT);
            }
            else {
               label.setAlignment(SWT.CENTER);
            }
         };
      };
             
      Button leftAlign = new Button(buttonGroup, SWT.RADIO);
      leftAlign.setText("Left");
      leftAlign.addSelectionListener(selectionListener);
      Button centerAlign = new Button(buttonGroup, SWT.RADIO);
      centerAlign.setText("Center");
      centerAlign.addSelectionListener(selectionListener);
      Button rightAlign = new Button(buttonGroup, SWT.RADIO);
      rightAlign.setText("Right");
      rightAlign.addSelectionListener(selectionListener);
 
      shell.open();
 
      while (!shell.isDisposed()) {
         if (!display.readAndDispatch()) {
            display.sleep();
         }
      }
      display.dispose();
   }
}

Programmatically selecting a JTable column

columnSelectionAllowed must be true and rowSelectionAllowed must be false.

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);
 
      // 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.setSelectionMode(ListSelectionModel.MULTIPLE_INTERVAL_SELECTION);
      table.setRowSelectionAllowed(false);
      table.setColumnSelectionAllowed(true);
 
      table.setColumnSelectionInterval(0, 0);
      table.addColumnSelectionInterval(2, 2);
 
      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;
   }
}

Using an SWT Sash

Sash is the Swing equivalent of a JSplitPane. It is a widget that can be dragged to resize two areas in a GUI.

Here’s an example of a Sash in a JFace application.

Category.java:

import java.util.*;

public class Category {
   private String name;
   private Category parent;
   private ArrayList categories = new ArrayList();
   private ArrayList links = new ArrayList();
   
   public Category(String name, Category parent) {
      this.name = name;
      this.parent = parent;
   }
   
   public void addSubCategory(Category category) {
      categories.add(category);
   }
   
   public void addLink(Link link) {
      links.add(link);
   }
   
   public ArrayList getSubCategories() {
      return categories;
   }
   
   public ArrayList getLinks() {
      return links;
   }
   
   public boolean hasSubCategories() {
      return categories.size() > 0;
   }
   
   public boolean hasLinks() {
      return links.size() > 0;
   }
   
   public String getName() {
      return name;
   }
   
   public Category getParent() {
      return parent;
   }
}

Link.java:

public class Link {
   private String url;
   
   public Link(String url) {
      this.url = url;
   }
   
   public String getUrl() {
      return url;
   }
}

CategoryTreeContentProvider.java:

import org.eclipse.jface.viewers.*;
import java.util.*;

public class CategoryTreeContentProvider implements ITreeContentProvider 
{
   public Object[] getChildren(Object element) {
      Category category = (Category) element;
      System.out.println(category.getName());
      
      ArrayList children = new ArrayList();
      children.addAll(category.getSubCategories());
      children.addAll(category.getLinks());
            
      if (children.size() == 0) {
         return new Object[0];
      }
      
      return children.toArray();
   }
   
   public Object[] getElements(Object element) {
      return getChildren(element);
   }
   
   public boolean hasChildren(Object element) {
      if (element instanceof Category) {
         Category category = (Category) element;
      
         return category.hasSubCategories() || category.hasLinks();
      }
      
      return false;
   }
   
   public Object getParent(Object element) {
      if (element instanceof Category) {
         return ((Category) element).getParent();
      }
      
      return null;
   }
   
   public void dispose() {
      
   }
   
   public void inputChanged(Viewer viewer, Object oldInput, Object newInput) {
      
   }
}

CategoryTreeLabelProvider.java:

import org.eclipse.jface.viewers.*;

public class CategoryTreeLabelProvider extends LabelProvider
{
   public String getText(Object element) {
      if (element instanceof Category) {
         return ((Category) element).getName();
      }
      else if (element instanceof Link) {
         return ((Link) element).getUrl();
      }
      
      return "" + element;
   }
}

Main.java:

import org.eclipse.jface.viewers.ISelectionChangedListener;
import org.eclipse.jface.viewers.IStructuredSelection;
import org.eclipse.jface.viewers.SelectionChangedEvent;
import org.eclipse.jface.viewers.TreeViewer;
import org.eclipse.jface.window.ApplicationWindow;
import org.eclipse.swt.SWT;
import org.eclipse.swt.custom.SashForm;
import org.eclipse.swt.layout.FormAttachment;
import org.eclipse.swt.layout.FormData;
import org.eclipse.swt.ole.win32.OLE;
import org.eclipse.swt.ole.win32.OleAutomation;
import org.eclipse.swt.ole.win32.OleControlSite;
import org.eclipse.swt.ole.win32.OleFrame;
import org.eclipse.swt.ole.win32.Variant;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Control;
import org.eclipse.swt.widgets.Display;

public class Main extends ApplicationWindow 
{
   private Category rootCategory;
   private OleAutomation automation = null;
   
   public Main() {
      super(null);
      
      // statically create categories
      rootCategory = new Category("Java", null);
      Category j2seCategory = new Category("J2SE", rootCategory);
      Link link = new Link("http://java.sun.com/j2se/");
      j2seCategory.addLink(link);
      Category j2eeCategory = new Category("J2EE", rootCategory);
      link = new Link("http://java.sun.com/j2ee/");
      j2eeCategory.addLink(link);
      Category j2meCategory = new Category("J2ME", rootCategory);
      link = new Link("http://java.sun.com/j2me/");
      j2meCategory.addLink(link);
      
      rootCategory.addSubCategory(j2seCategory);
      rootCategory.addSubCategory(j2eeCategory);
      rootCategory.addSubCategory(j2meCategory);
   }
   
   protected Control createContents(Composite parent) {
      SashForm sashForm = new SashForm(parent, SWT.HORIZONTAL | SWT.NULL);
      
      TreeViewer treeViewer = new TreeViewer(sashForm);
      treeViewer.setContentProvider(new CategoryTreeContentProvider());
      treeViewer.setLabelProvider(new CategoryTreeLabelProvider());
      treeViewer.setInput(rootCategory);
      
      createIEControl(sashForm);
      
      treeViewer.addSelectionChangedListener(new ISelectionChangedListener() {
         public void selectionChanged(SelectionChangedEvent event) {
            IStructuredSelection selection = (IStructuredSelection) event.getSelection();
            
            Object selectedObject = selection.getFirstElement();
            if (selectedObject instanceof Link) {
               goUrl(((Link) selectedObject).getUrl());  
            }
         }
      });
      
      return sashForm;
   }
   
   public static void main(String []args) {
      Main main = new Main();
      main.setBlockOnOpen(true);
      main.open();
      
      Display.getCurrent().dispose();
   }
   
   private void createIEControl(Composite parent) {     
      OleFrame frame = new OleFrame(parent, SWT.BORDER);
      FormData formData = new FormData();
      formData.top = new FormAttachment(0, 10);
      formData.left = new FormAttachment(0, 100);
      formData.right = new FormAttachment(100, 0);
      formData.bottom = new FormAttachment(100, -10);
      frame.setLayoutData(formData);
   
      OleControlSite controlSite = new OleControlSite(frame, SWT.NONE, "Shell.Explorer");
      controlSite.doVerb(OLE.OLEIVERB_SHOW);
      automation = new OleAutomation(controlSite);
      int[] rgdispid = automation.getIDsOfNames(new String[]{"GoHome"});
      int dispIdMember = rgdispid[0];
      automation.invoke(dispIdMember);
   }
   
   public void goUrl(String url) {
      int[] rgdispid = automation.getIDsOfNames(new String[]{"Navigate"});
      int dispIdMember = rgdispid[0];
      Variant[] rgvarg = new Variant[1]; // this is the URL parameter
      rgvarg[0] = new Variant(url);
      Variant pVarResult = automation.invoke(dispIdMember, rgvarg);      
   }   
}

Static imports in JDK 1.5

Static imports have been introduced in 1.5 to remove the burden of having to qualify constant names. With static imports, you import the static members from a class rather than the classes from a package.

For example, suppose we have a class Einstein that calculates the formula E=m*c*c.

comesusEinstein.java:

package com.esus;
 
public class Einstein
{
   public static long SPEED_OF_LIGHT = 299792458;
 
   public static double getEnergy(double mass) {
      return mass * SPEED_OF_LIGHT * SPEED_OF_LIGHT;
   }
}

Here is an example of how to use this class before 1.5.

Main.java:

import com.esus.Einstein;
 
public class Main
{
   public static void main(String []args) {
      double energy = Einstein.getEnergy(1.0);
   
      System.out.println("Speed of light is " + Einstein.SPEED_OF_LIGHT + " m/s");
      System.out.println("1KG of mass gives " + energy + " Joules");
   
   }
}

In 1.5, things would get simpler and more readable.

Main.java:

import static com.esus.Einstein.*;
 
public class Main
{
   public static void main(String []args) {
      double energy = getEnergy(1.0);
    
      System.out.println("Speed of light is " + SPEED_OF_LIGHT + " m/s");
      System.out.println("1KG of mass gives " + energy + " Joules");
   }
}

Notice that you can import static member constants as well as static methods.

Get a verbose output of the classes loaded by the VM

With JDK 1.5 java.lang.management package:

Main.java:

import java.lang.management.*;
 
public class Main
{
   public static void main(String []args) {
      ClassLoadingMBean mbean = ManagementFactory.getClassLoadingMBean();
      mbean.setVerbose(true);
       
      A a = new A();
   }
}
 
class A
{
}

outputs:

[Loaded A from file:/C:/my/jdk1.5/classloadingmbean/verbose/]
[Loaded java.lang.Shutdown from shared objects file]
[Loaded java.lang.Shutdown$Lock from shared objects file]

Converting an InputStream to a String

Main.java:

import java.io.*;
 
public class Main
{
   public static void main(String []args) throws IOException {
      if (args.length != 1) {
         System.out.println("Usage: java Main <file>");
         System.exit(1);
      }
      
      BufferedInputStream bis = new BufferedInputStream(new FileInputStream(args[0]));
      ByteArrayOutputStream baos = new ByteArrayOutputStream();
      
      long start = System.currentTimeMillis();
      int b;
      
      byte[] buf = new byte[2048];
      while ((b = bis.read(buf)) != -1) {
         baos.write(buf);
      }
      System.out.println("Time to read in file: " + (System.currentTimeMillis() - start));
      
      byte[] buffer = baos.toByteArray();
      
      String result = new String(buffer);  // or "new String(buffer, encoding)"

      System.out.println(result);
   }
}

Drawing a textured round filled 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.drawRoundRect(10, 40, 150, 150, 50, 30);
   }
 
   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:

Creating an OutputStream that manipulates the data written to it

Create a class that extends from FilterOutputStream and override the method write in which you convert the original value to a new value.

Following example introduces the ChangeCaseOutputStream which will convert any character to uppercase or lowercase depending on how you instantiated the class.

Main.java:

import java.io.*;
 
public class Main {
   public static void main(String args[]) {
      try {
         FileOutputStream fos = new FileOutputStream("test.out");
         ChangeCaseOutputStream ccos = new ChangeCaseOutputStream(
                                        ChangeCaseOutputStream.UPPERCASE, fos);
         ccos.write("hello, world!".getBytes());
         ccos.flush();
         ccos.close();
      }
      catch(FileNotFoundException e) {
         System.out.println(e);
      }
      catch(IOException e) {
         System.out.println(e);
      }
   }
}
 
class ChangeCaseOutputStream extends FilterOutputStream {
   public static final int LOWERCASE = 1;
   public static final int UPPERCASE = 2;
 
   private int conversionType;
 
   public ChangeCaseOutputStream(int conversionType, OutputStream in) {
      super(in);
 
      this.conversionType = conversionType;
   }
 
   public void write(int b) throws IOException {
      if (conversionType == LOWERCASE) {
         out.write((int) Character.toLowerCase((char) b));
      }
      else if (conversionType == UPPERCASE) {
         out.write((int) Character.toUpperCase((char) b));
      }
   }
}

Converting a String to a Reader

Java provides a StringReader class expressly for this purpose. java.io.StringReader has a constructor that takes a String argument.

import java.io.StringReader;
...
String myString = 'Testing 1 2 3...';
StringReader myStringReader = new StringReader(myString);
 
// Then, use standard Reader-reading techniques
// to access the Reader
int len = -1; // Number of chars read
char [] buf = new char[256]; // Characters read from Reader
try { 
   while ((len = myStringReader.read(buf, 0, 256)) != -1) {
      System.out.println('Next chunk from Reader is ' + (new String(buf, 0, len)));
   }
} catch (IOException ioe) {
   System.err.println("Error reading from Reader :" + e.getMessage());
}