[轉]Java Os 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.BorderLayout;
import java.util.Iterator;
import java.util.Properties;
import java.util.TreeSet;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;

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