Read and Write the properties file.

package au.com.d2klry.properties;

import java.io.BufferedWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FileWriter;
import java.io.IOException;
import java.util.Properties;

public class ReadPropertiesFile {

    public static void main(String[] args) {
        //First section is creating the properties file
        String fileName = "C:\\temp\\java\\properties.txt";
        String newFileName = "C:\\temp\\java\\newPropertiesFile.txt";
        try {
            File propertiesFile = new File(fileName);
            if(!propertiesFile.exists()){
                propertiesFile.createNewFile();
            }
            BufferedWriter writer = new BufferedWriter(new FileWriter(propertiesFile));
            writer.write("database_name=DB_TEST");
            writer.newLine();
            writer.write("database_host=localhost");
            writer.newLine();
            writer.write("database_port=50000");
            writer.newLine();
            writer.write("#database_username=scott");//Add a comment to properties file
            writer.newLine();
            writer.write("#database_password=tiger");
            writer.flush();
            writer.close();
            //End of creating properties file
        
            //Second part is reading the properties from the file, printing the properties to the console
            //and writing properties to the new file
            Properties properties = new Properties();
            properties.load(new FileInputStream(fileName));
            System.out.println("database_name -- > " + properties.getProperty("database_name"));
            System.out.println("database_host -- > " + properties.getProperty("database_host"));
            System.out.println("database_port -- > " + properties.getProperty("database_port"));
            //Property value will be null as it is not defined in the original properties file
            System.out.println("database_username -- > " + properties.getProperty("database_username"));
            
            properties.store(new FileOutputStream(newFileName), "File created by d2klry");
            
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}