Properties class in java

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Properties class:

Properties class is used to maintain the data in the key-value form. It takes both key and value as a string. Properties class is a subclass of Hashtable. It provides the methods to store properties in a properties file and to get the properties from the properties file. System.getProperties() returns the all system properties.

Properties class Constructor:

Method Description
Properties() It will create an empty property list with no default values.
Properties(Properties defaults) It will create an empty property list with the specified defaults.

Properties class Methods:

Method Description
public void load(Reader r) It will load data from the Reader object.
public void load(InputStream is) It will load data from the InputStream object
public void loadFromXML(InputStream in) It will load all of the properties represented by the XML document on the specified input stream into this properties table.
public String getProperty(String key) It will return value based on the key.
public String getProperty(String key, String defaultValue) It will search for the property with the specified key and return the value.
public void setProperty(String key, String value) It will call the put method of Hashtable.
public void list(PrintStream out) It will print the property list out to the specified output stream.
public void list(PrintWriter out) It will print the property list out to the specified output stream.
public Enumeration<?> propertyNames() It will return an enumeration of all the keys from the property list.
public Set<String> stringPropertyNames() It will return a set of keys from the property list where the key and its corresponding value are strings.
public void store(Writer w, String comment) It will write the properties in the writer object.
public void store(OutputStream os, String comment) It will write the properties in the OutputStream object.
public void storeToXML(OutputStream os, String comment) It will write the properties in the writer object for generating XML documents.
public void storeToXML(Writer w, String comment, String encoding) It will write the properties in the writer object for generating XML documents with the specified encoding.

Properties class example:

PropertiesTest.java

import java.util.Iterator;
import java.util.Properties;
import java.util.Set;
 
/**
 * This class is used to show the simple 
 * Properties class example.
 * @author w3schools
 */
public class PropetiesTest {
  public static void main(String[] args) {
 
	Properties prop = new Properties();
	Set props;
        String str;
 
	//Set the properties value
	prop.setProperty("database", "oracle10g");
	prop.setProperty("username", "system");
	prop.setProperty("password", "oracle");
 
	//Get key set
	props = prop.keySet(); 
 
	//Print the properties
        Iterator iterator = props.iterator();
        while(iterator.hasNext()) {
          str = (String) iterator.next();
          System.out.println("Prpperty: " + str + 
    	  ", Property Value: " + prop.getProperty(str));
       }
 
  }
}

Output:

Prpperty: password, Property Value: oracle
Prpperty: database, Property Value: oracle10g
Prpperty: username, Property Value: system

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Properties class example to write properties in a properties file and read it:

PropertiesTest.java

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Iterator;
import java.util.Properties;
import java.util.Set;
 
/**
 * This class is used to write properties in a properties 
 * file and read it.
 * @author w3schools
 */
public class PropetiesTest {
  public static void main(String[] args) {
 
	Properties prop = new Properties();
	Set props;
        String str;
 
	//Set the properties value
	prop.setProperty("database", "oracle10g");
	prop.setProperty("username", "system");
	prop.setProperty("password", "oracle");
 
	//Save properties to the project root folder
	try {
		OutputStream output = 
			new FileOutputStream("info.properties");
		prop.store(output, null);
		output.close();
	} catch (IOException e) {
		e.printStackTrace();
	}
 
	//Load the properties file
	Properties infoProp = new Properties();
	try {		
		InputStream input = 
			new FileInputStream("info.properties");
		infoProp.load(input);
		input.close();
	} catch (IOException e) {
		e.printStackTrace();
	}
 
	//Get key set
	props = infoProp.keySet(); 
 
	//Print the properties
       Iterator iterator = props.iterator();
       while(iterator.hasNext()) {
         str = (String) iterator.next();
         System.out.println("Prpperty: " + str + 
          ", Property Value: " + infoProp.getProperty(str));
      }
 
  }
}

Output:

Prpperty: password, Property Value: oracle
Prpperty: database, Property Value: oracle10g
Prpperty: username, Property Value: system

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Properties class example to get system properties:

PropertiesTest.java

import java.util.Iterator;
import java.util.Properties;
import java.util.Set;
 
/**
 * This class is used to get the system properties 
 * using Properties class.
 * @author w3schools
 */
public class PropetiesTest {
  public static void main(String[] args) {
	//Get system properties.
	Properties prop = System.getProperties(); 
	Set props;
        String str;
 
	//Get key set
	props = prop.keySet(); 
 
	//Print the properties
        Iterator iterator = props.iterator();
        while(iterator.hasNext()) {
          str = (String) iterator.next();
          System.out.println("Prpperty: " + str + 
         ", Property Value: " + prop.getProperty(str));
       }
 
  }
}

Output:

Prpperty: java.runtime.name, Property Value: 
Java(TM) SE Runtime Environment
Prpperty: sun.boot.library.path, Property Value: 
C:\Program Files (x86)\Java\jre7\bin
Prpperty: java.vm.version, Property Value: 23.25-b01
Prpperty: java.vm.vendor, Property Value: 
Oracle Corporation
Prpperty: java.vendor.url, Property Value: 
http://java.oracle.com/
Prpperty: path.separator, Property Value: ;
Prpperty: java.vm.name, Property Value: 
Java HotSpot(TM) Client VM
Prpperty: file.encoding.pkg, Property Value: sun.io
Prpperty: user.country, Property Value: IN
Prpperty: user.script, Property Value: 
Prpperty: sun.java.launcher, Property Value: SUN_STANDARD
...

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