Finding Java System Properties

// File: io/properties/SysPropList.java
// Description: Shows system properties.  This must be an application.
//              An applet can't get this information.
// Author: Fred Swartz
// Date:   2 Feb 2005

import java.awt.*;
import javax.swing.*;
import java.util.*;

/** Generic main program. */
public class SysPropList {
    public static void main(String[] args) {
        JFrame window = new JFrame("System Properties");
        window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        window.setContentPane(new SysPropListGUI());
        window.pack();
        window.setVisible(true);
    }
}

/** Panel to display the (limited) GUI intereface. */
class SysPropListGUI extends JPanel {
    JTextArea m_propertiesTA = new JTextArea(20, 40);

    /** Constructor sets layout, adds component(s), sets values*/
    public SysPropListGUI() {
        this.setLayout(new BorderLayout());
        this.add(new JScrollPane(m_propertiesTA), BorderLayout.CENTER);

        //... Add property list data to text area.
        Properties pr = System.getProperties();

	// TreeSet sorts keys
        TreeSet propKeys = new TreeSet(pr.keySet());  
        for (Iterator it = propKeys.iterator(); it.hasNext(); ) {
            String key = (String)it.next();
            m_propertiesTA.append("" + key + "=" + pr.get(key) + "n");
        }
    }
}