Fixing Security Issues with Java Code that Uses Command Line Argument

I need to fix the following code so that it follows proper input validation and data sanitization procedures. It takes a txt file of a list of email addresses from a command line argument.

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

public class Example {

    public static void main(String[] args) {
    String filename = args[0];
    BufferedReader inputStream = null;

    String fileLine;
    try {
        inputStream = new BufferedReader(new FileReader(filename));

        System.out.println("Email Addresses:");
        // Read one Line using BufferedReader
        while ((fileLine = inputStream.readLine()) != null) {
            System.out.println(fileLine);
        }
    } catch (IOException io) {
        System.out.println("File IO exception" + io.getMessage());
    } finally {
        // Need another catch for closing 
        // the streams          
        try {
            if (inputStream != null) {
                inputStream.close();
            }
        } catch (IOException io) {
            System.out.println("Issue closing the Files" + io.getMessage());
        }

    }
}