FileHandling Program Is Not Working?

this is my progarm

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Random;
public class FileHandlingDemo {

[code].....

As you can see my Intention is to save randoly generate Integer in the output file And this is not working but if I use Something like this

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
public class FileHandlingDemo {

[code].....

it's working fine reading that from Input.txt and writing that data in output.txt file. but not in first case Both file are in working directory already created.Where is wrong?