新人求教，关于没有main函数如何运行程序

最近在看Java核心技术 卷1。 里面的程序范例有的没有main函数，该如何运行呢？我用的是eclipse。

范例：
package plaf;

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.UIManager;

/**
* A frame with a button panel for changing look-and-feel
*/

public class PlafFrame extends JFrame {

private JPanel buttonPanel;
public PlafFrame()
{
buttonPanel = new JPanel();

UIManager.LookAndFeelInfo[] infos = UIManager.getInstalledLookAndFeels();
for(UIManager.LookAndFeelInfo info : infos)
makeButton(info.getName(), info.getClassName());

add(buttonPanel);
pack();
}


/**
* makes a button to change the pluggable look-and-feel
* @param name the button name
* @param plafName the name of the look-and-feel class
*/
void makeButton(String name, final String plafName)
{
//add button to panel

JButton button = new JButton(name);
buttonPanel.add(button);

//set button action

button.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent event)
{
//button action: switch to the new look-and-feel
try
{
UIManager.setLookAndFeel(plafName);
SwingUtilities.updateComponentTreeUI(PlafFrame.this);
pack();
}
catch(Exception e)
{
e.printStackTrace();
}
}
});
}
}