I just bumped into one of the error with file io. if you dont close fie handler, it wont write anything into file.

import java.io.*;
class FileWrite { 
public static void main(String args[]) { 
    // Create file 
    FileWriter fstream = new FileWriter("out.txt"); 
    BufferedWriter out = new BufferedWriter(fstream); 
    out.write("Hello Java"); 
    //Close the output stream 
}catch (Exception e){
//Catch exception if any 
System.err.println("Error: " + e.getMessage());