1. Make the constructor private so that it can not be instantiated from other class
2. Make the class final so that no other class can not extend this class.
3. Have a static method (e.g. getInstance()) to get the instance to access of the class and this method will retun the same object alwyas.

package test.easycodeforall.singletone;

import java.io.InputStream;
import java.util.Properties;

public final class PropManager {

	private static PropManager obj = new PropManager();
	private Properties prop = null;
	private String propFileName = "easycodeforall.properties";

	private PropManager() {
		loadProperties();
	}

	public void refreshCache() {
		loadProperties();
	}

	private void loadProperties() {
		try {
			prop = new Properties();
			InputStream propAsStream = this.getClass().getResourceAsStream(propFileName);
			prop.load(propAsStream);
		} catch (Exception ex) {
			System.out.println("Unable to load properties from " + propFileName + ". Exception=" + ex);
		}
	}

	public static PropManager getInstance() {
		return obj;
	}

	public String getProperty(String propertyName) {
		return prop.getProperty(propertyName);
	}
}
			
			

package test.easycodeforall.singletone;

public class TestSingletone {
	public static void main(String[] args) {
		System.out.println("Property Value=" + PropManager.getInstance().getProperty("base_folder_name"));
	}
}