Save and read hashmap to file?

Question

I want to write and read this hashmap to and from a txt file. This is what i have tried:

Main class:

    SaveRead xd = new SaveRead();
    HashMap <String,Integer>users = new HashMap<String,Integer>();

//e gets called on start

    private Object e() throws ClassNotFoundException, FileNotFoundException, IOException {
        return xd.readFile();
    }

    public void onFinish() {
          try {
            xd.saveFile(users);
        } catch (IOException e) {
        }
    }

//SaveRead class:

public class SaveRead implements Serializable{

    public void saveFile(HashMap<String, Integer> users) throws IOException{
    ObjectOutputStream outputStream = new ObjectOutputStream(new FileOutputStream("/Users/Konto/Documents/scores.txt"));
    outputStream.writeObject(users);
}

    public HashMap<String, Integer> readFile() throws ClassNotFoundException, FileNotFoundException, IOException{
        Object ii = new ObjectInputStream(new FileInputStream("/Users/Konto/Documents/scores.txt")).readObject();
        return (HashMap<String, Integer>) ii;
    }
}

Does this seem ok? When it try to read the file i dont get the desired result. Is there any better way going about it?

Answer 1

It is probably because you are not closing your streams, so the contents are not being flushed to disk. You can clean this up with the try-with-resources statement (available in Java 7+). Here's a compilable example:

public class SaveRead implements Serializable
{
    private static final String PATH = "/Users/Konto/Documents/scores.txt";

    public void saveFile(HashMap<String, Integer> users)
            throws IOException
    {
        try (ObjectOutputStream os = new ObjectOutputStream(new FileOutputStream(PATH))) {
            os.writeObject(users);
        }
    }

    public HashMap<String, Integer> readFile()
            throws ClassNotFoundException, IOException
    {
        try (ObjectInputStream is = new ObjectInputStream(new FileInputStream(PATH))) {
            return (HashMap<String, Integer>) is.readObject();
        }
    }

    public static void main(String... args)
            throws Exception
    {
        SaveRead xd = new SaveRead();

        // Populate and save our HashMap
        HashMap<String, Integer> users = new HashMap<>();
        users.put("David Minesote", 11);
        users.put("Sean Bright", 22);
        users.put("Tom Overflow", 33);

        xd.saveFile(users);

        // Read our HashMap back into memory and print it out
        HashMap<String, Integer> restored = xd.readFile();

        System.out.println(restored);
    }
}

Compiling and running this outputs the following on my machine:

{Tom Overflow=33, David Minesote=11, Sean Bright=22}