Grub de Bliek

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since Sep 09, 2003

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Recent posts by Grub de Bliek

invoking static methods on Class

If I had the class I could of course invoke a static method on it, like this:
com.company.tool.SomeThing.methodA();

But all I have is a String, ie "com.company.tool.SomeThing". Of course I must have the class first before I can invoke the static method. So how do I convert "com.company.tool.SomeThing" into com.company.tool.SomeThing

Because I want to invoke static methods, there's no point in instantiating the class. Also I prefer not to use reflection.
So my question is: is there a way to invoke static methods on a class I only have the class name of, preferably without using reflection?

19 years ago

Beginning Java

invoking static methods on Class

Hello,

I have a question I can't find the answer for. Maybe here I can find it.

In short the question is: can I invoke static methods of a certain class when I only have the Class object?

The situation is this:
1. I have a class com.company.tool.SomeThing with method public static void methodA() and field public static final String SOME_FIELD.
2. I do not want to instantiate this class.
3. I just have the class name: (com.company.tool.SomeThing)

What I'm trying is this:

I also want to retrieve the static public field but of course that won't work either. I really don't want to instantiate the class, but maybe I should consider to make it a Singleton with non static methods.

19 years ago

Beginning Java

TableSorter and Selection gives problems

Hello,

I'm trying to use a JTable in combination with the Sun TableSorter (v2.0 02/27/04). All works fine, but the user selection on the JTable disappears, when rows are added dynamically.

TableSorter provides a the method public int modelIndex(int viewIndex), so it's always possible to modify the correct row in the tablemodel when you only have an index of the view.
However, what I need is to retreive the index of the view, while I only have the index of the tableModel.

It works like this:
1. Before I add a row to the tableModel, I can get the selected rows from the JTable, and retrieve the indexes of the tableModel with the method modelIndex.
2. Then I add the row. Practically it is inserted in the view, because my Table is sorted. The row is added to the end of the TableModel, but inserted somewhere at an unknown place in the JTable.
3. I still have the tableModel indexes of the selected rows, and I just need to know their view indexes. But here I'm stuck. There's no way I can convert a modelIndex to a viewIndex.

By the way I'm using MULTIPLE_INTERVAL selections.

Here's the Sun TableSorter I'm using:

import java.awt.Color;
import java.awt.Component;
import java.awt.Graphics;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import javax.swing.Icon;
import javax.swing.JLabel;
import javax.swing.JTable;
import javax.swing.event.TableModelEvent;
import javax.swing.event.TableModelListener;
import javax.swing.table.AbstractTableModel;
import javax.swing.table.JTableHeader;
import javax.swing.table.TableCellRenderer;
import javax.swing.table.TableColumnModel;
import javax.swing.table.TableModel;
/**
* TableSorter is a decorator for TableModels; adding sorting
* functionality to a supplied TableModel. TableSorter does
* not store or copy the data in its TableModel; instead it maintains
* a map from the row indexes of the view to the row indexes of the
* model. As requests are made of the sorter (like getValueAt(row, col))
* they are passed to the underlying model after the row numbers
* have been translated via the internal mapping array. This way,
* the TableSorter appears to hold another copy of the table
* with the rows in a different order.
* <p/>
* TableSorter registers itself as a listener to the underlying model,
* just as the JTable itself would. Events recieved from the model
* are examined, sometimes manipulated (typically widened), and then
* passed on to the TableSorter's listeners (typically the JTable).
* If a change to the model has invalidated the order of TableSorter's
* rows, a note of this is made and the sorter will resort the
* rows the next time a value is requested.
* <p/>
* When the tableHeader property is set, either by using the
* setTableHeader() method or the two argument constructor, the
* table header may be used as a complete UI for TableSorter.
* The default renderer of the tableHeader is decorated with a renderer
* that indicates the sorting status of each column. In addition,
* a mouse listener is installed with the following behavior:
* <ul>
* <li>
* Mouse-click: Clears the sorting status of all other columns
* and advances the sorting status of that column through three
* values: {NOT_SORTED, ASCENDING, DESCENDING} (then back to
* NOT_SORTED again).
* <li>
* SHIFT-mouse-click: Clears the sorting status of all other columns
* and cycles the sorting status of the column through the same
* three values, in the opposite order: {NOT_SORTED, DESCENDING, ASCENDING}.
* <li>
* CONTROL-mouse-click and CONTROL-SHIFT-mouse-click: as above except
* that the changes to the column do not cancel the statuses of columns
* that are already sorting - giving a way to initiate a compound
* sort.
* </ul>
* <p/>
* This is a long overdue rewrite of a class of the same name that
* first appeared in the swing table demos in 1997.
*
* @author Philip Milne
* @author Brendon McLean
* @author Dan van Enckevort
* @author Parwinder Sekhon
* @version 2.0 02/27/04
*/
public class TableSorter extends AbstractTableModel {
protected TableModel tableModel;
public static final int DESCENDING = -1;
public static final int NOT_SORTED = 0;
public static final int ASCENDING = 1;
private static Directive EMPTY_DIRECTIVE = new Directive(-1, NOT_SORTED);
public static final Comparator COMPARABLE_COMAPRATOR = new Comparator() {
public int compare(Object o1, Object o2) {
return ((Comparable) o1).compareTo(o2);
}
};
public static final Comparator LEXICAL_COMPARATOR = new Comparator() {
public int compare(Object o1, Object o2) {
return o1.toString().compareTo(o2.toString());
}
};
private Row[] viewToModel;
private int[] modelToView;
private JTableHeader tableHeader;
private MouseListener mouseListener;
private TableModelListener tableModelListener;
private Map columnComparators = new HashMap();
private List sortingColumns = new ArrayList();
public TableSorter() {
this.mouseListener = new MouseHandler();
this.tableModelListener = new TableModelHandler();
}
public TableSorter(TableModel tableModel) {
this();
setTableModel(tableModel);
}
public TableSorter(TableModel tableModel, JTableHeader tableHeader) {
this();
setTableHeader(tableHeader);
setTableModel(tableModel);
}
private void clearSortingState() {
viewToModel = null;
modelToView = null;
}
public TableModel getTableModel() {
return tableModel;
}
public void setTableModel(TableModel tableModel) {
if (this.tableModel != null) {
this.tableModel.removeTableModelListener(tableModelListener);
}
this.tableModel = tableModel;
if (this.tableModel != null) {
this.tableModel.addTableModelListener(tableModelListener);
}
clearSortingState();
fireTableStructureChanged();
}
public JTableHeader getTableHeader() {
return tableHeader;
}
public void setTableHeader(JTableHeader tableHeader) {
if (this.tableHeader != null) {
this.tableHeader.removeMouseListener(mouseListener);
TableCellRenderer defaultRenderer = this.tableHeader.getDefaultRenderer();
if (defaultRenderer instanceof SortableHeaderRenderer) {
this.tableHeader.setDefaultRenderer(((SortableHeaderRenderer) defaultRenderer).tableCellRenderer);
}
}
this.tableHeader = tableHeader;
if (this.tableHeader != null) {
this.tableHeader.addMouseListener(mouseListener);
this.tableHeader.setDefaultRenderer(new SortableHeaderRenderer(this.tableHeader.getDefaultRenderer()));
}
}
public boolean isSorting() {
return sortingColumns.size() != 0;
}
private Directive getDirective(int column) {
for (int i = 0; i < sortingColumns.size(); i++) {
Directive directive = (Directive) sortingColumns.get(i);
if (directive.column == column) {
return directive;
}
}
return EMPTY_DIRECTIVE;
}
public int getSortingStatus(int column) {
return getDirective(column).direction;
}
private void sortingStatusChanged() {
clearSortingState();
fireTableDataChanged();
if (tableHeader != null) {
tableHeader.repaint();
}
}
public void setSortingStatus(int column, int status) {
Directive directive = getDirective(column);
if (directive != EMPTY_DIRECTIVE) {
sortingColumns.remove(directive);
}
if (status != NOT_SORTED) {
sortingColumns.add(new Directive(column, status));
}
sortingStatusChanged();
}
protected Icon getHeaderRendererIcon(int column, int size) {
Directive directive = getDirective(column);
if (directive == EMPTY_DIRECTIVE) {
return null;
}
return new Arrow(directive.direction == DESCENDING, size, sortingColumns.indexOf(directive));
}
private void cancelSorting() {
sortingColumns.clear();
sortingStatusChanged();
}
public void setColumnComparator(Class type, Comparator comparator) {
if (comparator == null) {
columnComparators.remove(type);
} else {
columnComparators.put(type, comparator);
}
}
protected Comparator getComparator(int column) {
Class columnType = tableModel.getColumnClass(column);
Comparator comparator = (Comparator) columnComparators.get(columnType);
if (comparator != null) {
return comparator;
}
if (Comparable.class.isAssignableFrom(columnType)) {
return COMPARABLE_COMAPRATOR;
}
return LEXICAL_COMPARATOR;
}
private Row[] getViewToModel() {
if (viewToModel == null) {
int tableModelRowCount = tableModel.getRowCount();
viewToModel = new Row[tableModelRowCount];
for (int row = 0; row < tableModelRowCount; row++) {
viewToModel[row] = new Row(row);
}
if (isSorting()) {
Arrays.sort(viewToModel);
}
}
return viewToModel;
}
public int modelIndex(int viewIndex) {
return getViewToModel()[viewIndex].modelIndex;
}
private int[] getModelToView() {
if (modelToView == null) {
int n = getViewToModel().length;
modelToView = new int[n];
for (int i = 0; i < n; i++) {
modelToView[modelIndex(i)] = i;
}
}
return modelToView;
}
// TableModel interface methods
public int getRowCount() {
return (tableModel == null) ? 0 : tableModel.getRowCount();
}
public int getColumnCount() {
return (tableModel == null) ? 0 : tableModel.getColumnCount();
}
public String getColumnName(int column) {
return tableModel.getColumnName(column);
}
public Class getColumnClass(int column) {
return tableModel.getColumnClass(column);
}
public boolean isCellEditable(int row, int column) {
return tableModel.isCellEditable(modelIndex(row), column);
}
public Object getValueAt(int row, int column) {
return tableModel.getValueAt(modelIndex(row), column);
}
public void setValueAt(Object aValue, int row, int column) {
tableModel.setValueAt(aValue, modelIndex(row), column);
}
// Helper classes
private class Row implements Comparable {
private int modelIndex;
public Row(int index) {
this.modelIndex = index;
}
public int compareTo(Object o) {
int row1 = modelIndex;
int row2 = ((Row) o).modelIndex;
for (Iterator it = sortingColumns.iterator(); it.hasNext() :wink: {
Directive directive = (Directive) it.next();
int column = directive.column;
Object o1 = tableModel.getValueAt(row1, column);
Object o2 = tableModel.getValueAt(row2, column);
int comparison = 0;
// Define null less than everything, except null.
if (o1 == null && o2 == null) {
comparison = 0;
} else if (o1 == null) {
comparison = -1;
} else if (o2 == null) {
comparison = 1;
} else {
comparison = getComparator(column).compare(o1, o2);
}
if (comparison != 0) {
return directive.direction == DESCENDING ? -comparison : comparison;
}
}
return 0;
}
}
private class TableModelHandler implements TableModelListener {
public void tableChanged(TableModelEvent e) {
// If we're not sorting by anything, just pass the event along.
if (!isSorting()) {
clearSortingState();
fireTableChanged(e);
return;
}
// If the table structure has changed, cancel the sorting; the
// sorting columns may have been either moved or deleted from
// the model.
if (e.getFirstRow() == TableModelEvent.HEADER_ROW) {
cancelSorting();
fireTableChanged(e);
return;
}
// We can map a cell event through to the view without widening
// when the following conditions apply:
//
// a) all the changes are on one row (e.getFirstRow() == e.getLastRow()) and,
// b) all the changes are in one column (column != TableModelEvent.ALL_COLUMNS) and,
// c) we are not sorting on that column (getSortingStatus(column) == NOT_SORTED) and,
// d) a reverse lookup will not trigger a sort (modelToView != null)
//
// Note: INSERT and DELETE events fail this test as they have column == ALL_COLUMNS.
//
// The last check, for (modelToView != null) is to see if modelToView
// is already allocated. If we don't do this check; sorting can become
// a performance bottleneck for applications where cells
// change rapidly in different parts of the table. If cells
// change alternately in the sorting column and then outside of
// it this class can end up re-sorting on alternate cell updates -
// which can be a performance problem for large tables. The last
// clause avoids this problem.
int column = e.getColumn();
if (e.getFirstRow() == e.getLastRow()
&& column != TableModelEvent.ALL_COLUMNS
&& getSortingStatus(column) == NOT_SORTED
&& modelToView != null) {
int viewIndex = getModelToView()[e.getFirstRow()];
fireTableChanged(new TableModelEvent(TableSorter.this, viewIndex, viewIndex, column, e.getType()));
return;
}
// Something has happened to the data that may have invalidated the row order.
clearSortingState();
fireTableDataChanged();
return;
}
}
private class MouseHandler extends MouseAdapter {
public void mouseClicked(MouseEvent e) {
JTableHeader h = (JTableHeader) e.getSource();
TableColumnModel columnModel = h.getColumnModel();
int viewColumn = columnModel.getColumnIndexAtX(e.getX());
int column = columnModel.getColumn(viewColumn).getModelIndex();
if (column != -1) {
int status = getSortingStatus(column);
if (!e.isControlDown()) {
cancelSorting();
}
// Cycle the sorting states through {NOT_SORTED, ASCENDING, DESCENDING} or
// {NOT_SORTED, DESCENDING, ASCENDING} depending on whether shift is pressed.
status = status + (e.isShiftDown() ? -1 : 1);
status = (status + 4) % 3 - 1; // signed mod, returning {-1, 0, 1}
setSortingStatus(column, status);
}
}
}
private static class Arrow implements Icon {
private boolean descending;
private int size;
private int priority;
public Arrow(boolean descending, int size, int priority) {
this.descending = descending;
this.size = size;
this.priority = priority;
}
public void paintIcon(Component c, Graphics g, int x, int y) {
Color color = c == null ? Color.GRAY : c.getBackground();
// In a compound sort, make each succesive triangle 20%
// smaller than the previous one.
int dx = (int) (size / 2 * Math.pow(0.8, priority));
int dy = descending ? dx : -dx;
// Align icon (roughly) with font baseline.
y = y + 5 * size / 6 + (descending ? -dy : 0);
int shift = descending ? 1 : -1;
g.translate(x, y);
// Right diagonal.
g.setColor(color.darker());
g.drawLine(dx / 2, dy, 0, 0);
g.drawLine(dx / 2, dy + shift, 0, shift);
// Left diagonal.
g.setColor(color.brighter());
g.drawLine(dx / 2, dy, dx, 0);
g.drawLine(dx / 2, dy + shift, dx, shift);
// Horizontal line.
if (descending) {
g.setColor(color.darker().darker());
} else {
g.setColor(color.brighter().brighter());
}
g.drawLine(dx, 0, 0, 0);
g.setColor(color);
g.translate(-x, -y);
}
public int getIconWidth() {
return size;
}
public int getIconHeight() {
return size;
}
}
private class SortableHeaderRenderer implements TableCellRenderer {
private TableCellRenderer tableCellRenderer;
public SortableHeaderRenderer(TableCellRenderer tableCellRenderer) {
this.tableCellRenderer = tableCellRenderer;
}
public Component getTableCellRendererComponent(JTable table,
Object value, boolean isSelected, boolean hasFocus, int row,
int column) {
Component c = tableCellRenderer.getTableCellRendererComponent(table, value, isSelected, hasFocus, row, column);
if (c instanceof JLabel) {
JLabel l = (JLabel) c;
l.setHorizontalTextPosition(JLabel.LEFT);
int modelColumn = table.convertColumnIndexToModel(column);
l.setIcon(getHeaderRendererIcon(modelColumn, l.getFont().getSize()));
}
return c;
}
}
private static class Directive {
private int column;
private int direction;
public Directive(int column, int direction) {
this.column = column;
this.direction = direction;
}
}
}

[ June 23, 2005: Message edited by: Grub de Bliek ]

19 years ago

Swing / AWT / SWT

Need help on design of Swing application

Hello,

I'm having a problem here with the design of my Swing app. It is a typical application with a JTree for navigation on the left, and a screen on the right.
Each node in the tree implements an interface with the method JPanel getScreen(), so I'm able to set the screen on the right with the correct screen when selected. This way I can add any node with an own screen to the navigation tree.

Because I want to keep View and Model separated, each Node in the tree contains a DataObject. Lets say my application displays files and directories, then I have a DirectoryNode containing a DirectoryDAO, and a FileNode containing a FileDAO. When a node is clicked, details of the object belonging to it are shown in the screen on right.
All looks good to me so far. I have a lot of different types of DataObjects displayed in my application.

However my problem is that I've several objects that must be available for all of them. For example, because I want to be able to show modal dialogs, I need to have the top level JFrame available for each node. Also, because I must be able to add and remove nodes, I must be able to access the navigation tree from any node. Those are the View objects that must be available.

Also, my DataObjects are nested. Like with Directories and Files, each File or Directory must be able to access the properties of its parent directories. Those are the Model objects that must be available to the child DataObjects.

I've been trying to implement this using a "Context" object which I'm passing to the constructor of any child node added to the tree. Context just contains the JFrame, the Tree, and the parent DataObject. Any new DataObject in the tree just adds itself to the Context and passes the context to its children.

However this is a far from perfect solution.
1. First of all, Model and View are mixed in my Context object, which I don't want.
2. Secondly, not all properties of Context can be final because after creation they must be set by the child data objects. This means they can be null, or set with wrong values.

I really don't know how to handle this, and my whole beautiful application gets messed up right now. Does anyone have some suggestions for me how to solve this?

Thank you very, very much.
[ June 21, 2005: Message edited by: Grub de Bliek ]

19 years ago

Swing / AWT / SWT

JDBC summary's, surveys, resources on the web?

Hi,

I'm looking for a couple of good locations on the web where I can find summary's and surveys of (JDBC) databases.

I do not use db's frequently, but when I need to do something with it I always spend hours on the web looking fo specs and features, compatible datatypes, XA support, etc.

99% of the pages I find are commercial advertisement. Specs and features are hard to find, surveys of more than one db even harder.

If anyone can help me with this, I would be very, very grateful..

grtz,
Gerben

20 years ago

JDBC and Relational Databases

To the authors 2

What experience/knowledge is required when I want to go for the SCBCD using your material? Do I need SCJP at least? Or SCWCD?
Is it just a similator and do I need another book for the theory?
How many questions are in the simulator?
Is the JMX included in the SCBCD?

21 years ago

EJB Certification (OCEEJBD)

2 simple questions..

Ok thanks!
I knew I could put a try/catch block in a finally block, but I was thinking that prevented the finally block from executing. I see that isn't correct, if an exception occurs in a finally block, the rest of the code is executed anyway.

21 years ago

JDBC and Relational Databases

2 simple questions..

1. When I close my statement and my connection, do I lose the ResultSet I just queried?
2. Look at this piece of code:
//querying code....
} catch(SQLException e) {
e.printStackTrace();
} finally {
if (statement != null)
statement.close();
if (connection != null)
connection.close();
}
}
This can't be done cuz both close() methods must be handled with an SQLException as well. The way I see it is that I *must* catch that SQLException one level higher, but I don't want that. All my exceptions must be handled in this method. Is there a way to solve this?

21 years ago

JDBC and Relational Databases

Linux Java - done right

But isn't it right that Red Hat Linux is the officially supported Linux platform?
From http://java.sun.com/j2ee/1.4/download-dr.html:
The following table lists the required version of J2SE for each operating system that is supported with this release of J2EE:
SolarisTM SPARC 8, 9
Windows 2000 Professional SP3+
Windows XP Professional SP1+
Windows 2000 Server SP3+
Windows Server 2003
Linux Redhat, v8.0
I have a couple of questions about this. I installed an old version of Red Hat, 7.3. I'm totally no Linux expert, so the question is quite easy:
How can I upgrade to the latest Red Hat release?
Do I have to buy a new release, or can I download it somewhere. Is it enough to install a new kernel, or doesn't that upgrade the whole release?
I've been looking for some time now, but the answers on the simplest questions are always hard to find.
And can I also run all Java 2 Enterprise Platform applications like JBoss and Bea Weblogic on other Linux release like Suse?

21 years ago

GNU/Linux

Dating Design Patterns book promo (written by me, Solveig, female girl)

I have that book too! What page is the pic?

21 years ago

OO, Patterns, UML and Refactoring

Confused about patterns?

I think it's wrong to study the working of the design pattern itself, you should only study the situation it could be applied on.
Then, when you're developing you will sometimes run in situations difficult to solve. Then you will recognize those difficulties and think, "Hey! Doesn't the singleton solve this problem? How does a singleton work?"
And then you're gonna study the design pattern and implement it. This way you won't use much design patterns, but the number will grow when you get more experienced, and recognize more situations. Try to avoid to write your app around a design pattern, rather write your app and then refactor it with a design pattern.

21 years ago

OO, Patterns, UML and Refactoring

What design for XmlFileReader?

It certainly does! Nice piece of work there...
I'm gonna try to use this in my code. Thx!

21 years ago

OO, Patterns, UML and Refactoring

What design for XmlFileReader?

Hey,
I'm creating a simple GUIBuilder that builds a GUI from a XML file. I've build it working a few times, but I don't like the design. Number 1 uses one big class that gets the File and returns two references to the mainWindow and the GUIModel. Number 2 uses a class GUIBuilder that calls methods from a class XMLFileReader to get the components out of the XMLFile. But, because the GUIBuilder adds the components one by one on the GUI and in the GUIModel, I can only call static methods in de class XMLFileReader.
It works, but I'm not happy with it, because it's too big already and I use only a couple of components yet.
Those are my requirements:
- I must read a component from the xml file, check it's attributetype, and create the component, I also read attr's like size and position from it's child components and set them.
- I must be able to get a component from the GUI on its unique id, so I need a model with an id-reference mapping(of the component). Especially because I'm gonna add some event handling later).
Problem is that I always tend to functional programming (with the static methods). Maybe someone in here can give me a few hints on how to solve this.

21 years ago

OO, Patterns, UML and Refactoring

JTable with Model Filters

Apparently you TableModelFilter doesn't work correct. Can't say what's wrong with it.
Here's a TableSorter that works with indexes. I once implemented a TableFilter that looked alot like a TableSorter, so this might be a good example.
http://www2.gol.com/users/tame/swing/examples/JTableExamples5.html

21 years ago

Swing / AWT / SWT

JTable and JCheckboxes

tried a revalidate()?

21 years ago

Swing / AWT / SWT