import java.io.*;
import java.util.*;

public class PropertyFiles {
	
	public void addProperty(File propFileName, String key, String value) throws Exception{
        			
		//loading an existing property file in a properties object
		FileInputStream fin = new FileInputStream(propFileName);
		Properties props = new Properties();
		props.load(fin);
		fin.close();
		
		//adding a proprty (key=value) to a properties obj
		props.setProperty(key, value); 			
	
		//save this new value to the original property file
		FileOutputStream fout = new FileOutputStream(propFileName);
		props.store(fout, "Modified Property File");
		fout.close();
		
	}	
	
	public static void main(String a[]) throws Exception {
		String dirPath = "e:/projects/test";		
		File dirFile = new File(dirPath);
		PropertyFiles file = new PropertyFiles();
		
		if(dirFile.isDirectory()) {
			
			File[] propFiles =  dirFile.listFiles(new PropertyFileFilter());
		
			for(int i=0; i
file.addProperty(propFiles[i], "hello", "value");	
			}			
			
		}//end if
	
	}//main

	static class PropertyFileFilter implements FileFilter {
		public boolean accept(File pathname)  {
			if(pathname.getName().endsWith("properties")) {
				return true;
			}
			
			return false;			
		}
	}
	
}//end class