What is a Java property category?

[Viensterrr]

I am new to the Java. I want to know what is a Java Property Category?Can someone explain me by giving an example. Also tell me the purpose of using them.? Since I am new to the Java, very simple and right answers are warmly welcomed.!

[Warner]

I think that you want to know about the Java Property class. To save and restore the properties for a program of Java, the function of the java.util.Properties class is used. Also using the java.util.Preferences will be easier. The java.util.Properties class stores and loads key/value pairs from a file, and manages them in memory. I am giving an example code for creating a new Properties table and I am assigning a string value to three different keys. Here is the code for that :

Properties props = new Properties(); 
props.setProperty("recursiveSearch", "true");
props.setProperty("maxLevel", "7");
props.setProperty("fileName", "C:\temp\work.html");

[void]

You can use the Properties .store method for storing a Properties table in a file. This method will write the properties to the output stream, with a header line from the String parameter.

boolean recursiveSearch;
String noCopyPattern;
int maxLevel;
. . .
try {
  OutputStream propOut = new FileOutputStream(
            new File("props.stat"));
}catch (. . .

[CodGuru]

I think that you are asking about the System Properties. I have explained how to get the System Properties. You can get only one property at a time by supplying the key in a call to System.getProperty().

• String System.getProperty(String key, String default) - This property Returns the value of property key as a string.
• String System.getProperty(String key) - This property returns the value of property key as a String.
• Properties System.getProperties() - This property returns a Properties object which has the value of all the properties.

[Allan.d]

You can use the following program for displaying a list of System Properties.

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

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);
    }
}

class SysPropListGUI extends JPanel {
    JTextArea m_propertiesTA = new JTextArea(20, 40);

    public SysPropListGUI() {
        this.setLayout(new BorderLayout());
        this.add(new JScrollPane(m_propertiesTA), BorderLayout.CENTER);

        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");
        }
    }
}