Java – Read/write Properties from/to .properties file

https://grokonez.com/java/java-read-write-properties-object-properties-file-properties-file

Java – Read/write Properties from/to .properties file

In the post, we show how to read/write Properties object from/to Properties File (.properties file).

I. Java - Write Properties object to Properties File

1. Properties store() method

We use java.util.Properties.store() methods:

// 1.
public void store(OutputStream out,
                      String comments)
                throws IOException

-> Writes this property list (key and element pairs) in this Properties table 
to the output stream in a format suitable for loading into a Properties table using the load(InputStream) method.

// 2.
public void store(Writer writer,
                    String comments)
                throws IOException
                
-> Writes this property list (key and element pairs) in this Properties table 
to the output character stream in a format suitable for using the load(Reader) method.

2. Program - write Properties to File

package com.javasampleapproach.propertiesfile;

import java.io.FileOutputStream;
import java.io.FileWriter;
import java.io.IOException;
import java.io.OutputStream;
import java.io.Writer;
import java.util.Properties;

public class JavaWriteProperties2File {
    public static void main(String[] args) {
        Properties properties = new Properties();
        properties.put("db.username", "username");
        properties.put("db.password", "password");
        properties.put("db.driver", "org.postgresql.Driver");
        properties.put("db.url", "jdbc:postgresql://localhost/testdb");
        
        /*
         *  Approach 1: 
         *  use -> 'java.util.Properties.store(OutputStream out, String comments) throws IOException'
         */
        String propertiesFile = System.getProperty("user.dir") + "\\file.properties";
        try(OutputStream propertiesFileWriter = new FileOutputStream(propertiesFile)){
            properties.store(propertiesFileWriter, "save to properties file");
        }catch(IOException ioe){
            ioe.printStackTrace();
        }
        
        /*
         *  Approach 2: 
         *  use -> 'java.util.Properties.store(Writer writer, String comments) throws IOException'
         */
        propertiesFile = System.getProperty("user.dir") + "\\file_1.properties";
        try(Writer propertiesFileWriter = new FileWriter(propertiesFile)){
            properties.store(propertiesFileWriter, "save to properties file");
        }catch(IOException ioe){
            ioe.printStackTrace();
        }
    }
}

-> .properties output file:

More at:

https://grokonez.com/java/java-read-write-properties-object-properties-file-properties-file

Java – Read/write Properties from/to .properties file