Table Format Renderers

JTable uses renderers to display data in each cell of the table. This allows for data to easily be displayed in different formats in any given cell.  However, the table only provides support for a few basic renderers:

• Boolean – rendered with a check box.
• Number – rendered by a right-aligned label .
• Date – rendered by a label.
• Icon – rendered by a centered label.
• Object – rendered by a label that displays the object’s string value.

Not much to choose from when you want to jazz up the display of your data. Fortunately we can easily create a renderer which will allow us to format the data in various ways.

Most code examples of custom rendering show code that overrides the getTableCellRendererComponent(…) method to update the properties of the renderer directly. For simple formatting we will take a different approach, as we will be overriding the setValue(…) method. Using this approach we can take advantage of the Format class and the formatting capabilities of its sub classes. For example to create a simple date renderer you could do:

public class YMDRenderer extends DefaultTableCellRenderer
{
private Format formatter = new SimpleDateFormat("yy/MM/dd");

public void setValue(Object value)
{
//  Format the Object before setting its value in the renderer

try
{
if (value != null)
value = formatter.format(value);
}
catch(IllegalArgumentException e) {}

super.setValue(value);
}
}

However, after a while you may get tired of creating custom rendering classes so you can instead use the FormatRenderer class. This class will use the Format class and its subclasses, specifically the DateFormat and NumberFormat classes, to provide flexible formatting of your data. The FormatRenderer will require only a single parameter, the Format object to be used to format the data. For example:

SimpleDateFormat format = new SimpleDateFormat("yy/MM/dd");
TableCellRenderer renderer = new FormatRenderer( format );

A convenience class, NumberRenderer, was also created that simply uses right alignment for the renderer. In both classes, convenience static methods have been created to return common renderers. The breakdown is as follows:

• FormatRenderer
  • getDateTimeRenderer
  • getTimeRenderer
  • NumberRenderer
    • getCurrencyRenderer
    • getIntegerRenderer
    • getPercentRenderer

The following code sample was used to generate the table pictured in the image:

TableColumnModel m = table.getColumnModel();
m.getColumn(0).setCellRenderer(FormatRenderer.getDateTimeRenderer());
m.getColumn(1).setCellRenderer(FormatRenderer.getTimeRenderer());
m.getColumn(2).setCellRenderer(NumberRenderer.getPercentRenderer());
m.getColumn(3).setCellRenderer(NumberRenderer.getCurrencyRenderer());

 

Get The Code

FormatRenderer.java
NumberRenderer.java

Related Reading

Concepts: Editor and Renderers
Java API: java.text.Format