Updating property value in properties file without deleting other values

Content of First.properties:

name=elango
country=india
phone=12345

I want change country from india to america. This is my code:

import java.io.*;
public class UpdateProperty 
{
	public static void main(String args[]) throws Exception 
	{ 	
		FileOutputStream out = new FileOutputStream("First.properties");
		FileInputStream in = new FileInputStream("First.properties");
		Properties props = new Properties();
		props.load(in);
		in.close();
		props.setProperty("country", "america");
		props.store(out, null);
		out.close();
	} 
}

Output content of First.properties:

country=america

The other properties are deleted. I want update a particular property value, without deleting the other properties.

Open the output stream and store properties after you have closed the input stream.

FileInputStream in = new FileInputStream("First.properties");
Properties props = new Properties();
props.load(in);
in.close();
        
FileOutputStream out = new FileOutputStream("First.properties");
props.setProperty("country", "america");
props.store(out, null);
out.close();

You can use Apache Commons Configuration library. The best part of this is, it won't even mess up the properties file and keeps it intact (even comments).

Javadoc

PropertiesConfiguration conf = new PropertiesConfiguration("propFile.properties");
conf.setProperty("key", "value");
conf.save();    

Properties prop = new Properties();
prop.load(...); // FileInputStream 
prop.setProperty("key", "value");
prop.store(...); // FileOutputStream