Using Properties in JavaUsing Properties in Java

Java has great API for working with properties.
In this post I am going to show example which shows how to work with properties with Properties class.
In my work I very often use properties and xml files for configuration.
Example will show how to load properties from property file,how to read them,how to write to other property file and how to set the new properties.
Properties need to put in file with properties extension.
Property file in this example is located under current working directory.
default.properties:

dirName = E:/propertiesExamplefileName = noname.properties

and code:

import java.io.File;import java.io.FileInputStream;import java.io.FileNotFoundException;import java.io.FileOutputStream;import java.io.IOException;import java.util.Properties;public class Main{ private static String dirName; private static String fileName; private static Properties properties; public static void main(String[] args) throws IOException{ properties = loadProperties("default.properties"); writeProperties(); System.out.println("Done"); }  private static Properties loadProperties(String fileName) throws IOException{ Properties defaultProps = new Properties(); FileInputStream in = new FileInputStream(fileName); defaultProps.load(in); in.close(); readProperties(defaultProps); return defaultProps; }  private static void readProperties(Properties defaultProperties){ dirName = defaultProperties.getProperty("dirName"); fileName = defaultProperties.getProperty("fileName"); }  private static void writeProperties() throws FileNotFoundException,IOException{ Properties newProperties = new Properties(); File f = new File(dirName); f.mkdir(); File newFile = new File(f,fileName); FileOutputStream out = new FileOutputStream(newFile); setProperties(newProperties); newProperties.store(out,"My comments"); out.close(); }  private static void setProperties(Properties newProperties){ newProperties.setProperty("authorName","The Developer's Info"); }}

As you can see it is very easy. As usual all methods in example are simple but they show all what you need to know. If you want to know more about Properties please read API.

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