Java Properties File Examples

1. Write to properties file

Set the property value, and write it into a properties file named “Data.properties“.

Navigation for creating the properties file:-
-> Right click on the package.
-> Go to “new”, Select the option “others”.
-> Expand “general”.
-> Select the option “file”.
-> Click on next.
-> Specify the desired file name with “.properties” extension, click on finish.

import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Properties;

public class App 
{
    public static void main( String[] args )
    {
    	Properties prop = new Properties();

    	try {
    		//set the properties value
    		prop.setProperty("database", "localhost");
    		prop.setProperty("dbuser", "mytest");
    		prop.setProperty("dbpassword", "password");

    		//save properties to project root folder
    		prop.store(new FileOutputStream("Data.properties"), null);

    	} catch (IOException ex) {
    		ex.printStackTrace();
        }
    }
}

Output

Data.properties

dbpassword=password
database=localhost
dbuser=mytest

P.S If file path is not specified, then this properties file will be stored in your project root folder.

2. Load a properties file

Load a properties file from the file system and retrieved the property value.

 
import java.io.FileInputStream;
import java.io.IOException;
import java.util.Properties;

public class App 
{
    public static void main( String[] args )
    {
    	Properties prop = new Properties();

    	try {
               //load a properties file
    		prop.load(new FileInputStream("Data.properties"));

               //get the property value and print it out
                System.out.println(prop.getProperty("database"));
    		System.out.println(prop.getProperty("dbuser"));
    		System.out.println(prop.getProperty("dbpassword"));

    	} catch (IOException ex) {
    		ex.printStackTrace();
        }

    }
}

Output

localhost
mytest
password

3. Load a properties file from classpath

Load a properties file named “Data.properties” from project classpath, and retrieved the property value.

 
import java.io.FileInputStream;
import java.io.IOException;
import java.utilutil.Properties;

public class App 
{
    public static void main( String[] args )
    {
    	Properties prop = new Properties();

    	try {
               //load a properties file from class path, inside static method
    		prop.load(App.class.getClassLoader().getResourceAsStream("Data.properties");));

               //get the property value and print it out
                System.out.println(prop.getProperty("database"));
    		System.out.println(prop.getProperty("dbuser"));
    		System.out.println(prop.getProperty("dbpassword"));

    	} catch (IOException ex) {
    		ex.printStackTrace();
        }

    }
}

For non-static method, use this :

prop.load(getClass().getClassLoader().getResourceAsStream("Data.properties");));