CODEWITHSUNDEEP
javafilehashmap
Adam_G
Adam_G

Reputation: 7879

Java: Ideal file format to store a hashmap in?

I need to save an arraylist of hashmaps to an external file. I can use any format expect for a text file, because the program is set to ignore text files (specially, anything with a .txt extension). The hashmaps are pretty straightforward, just words with counts of those words. What is the ideal file format to store this in?

Upvotes: 1

Views: 1015

Answers (2)

Peter
Peter

Reputation: 679

You could use serialization:

    ObjectOutputStream stream = null;
    try
    {
        File f = new File(filename);
        stream = new ObjectOutputStream(new FileOutputStream(f));
        stream.writeObject(your_arraylist);
    }
    catch (IOException e)
    {
        // Handle error
    }
    finally
    {
        if (stream != null)
        {
            try
            {
                stream.close();
            }
            catch (Exception e) {}
        }
    }

And read it in using:

    ObjectInputStream stream = null;
    try
    {
        stream = new ObjectInputStream(new FileInputStream(f));
        your_arrayList = (your_arrayList type here)stream.readObject();
    }
    catch (Throwable t)
    {
        // Handle error
    }
    finally
    {
        if (stream != null)
        {
            try
            {
                stream.close();
            }
            catch (Exception e) {}
        }
    }

Upvotes: 1

BalusC
BalusC

Reputation: 1108922

You could use java.util.Properties.

Properties properties = new Properties();
properties.putAll(yourMap); // You could also just use Properties in first place.

try (OutputStream output = new FileOutputStream("/foo.properties")) {
    properties.store(output, null);
}

You can read it later by

Properties properties = new Properties();

try (InputStream input = new FileInputStream("/foo.properties")) {
    properties.load(input);
}

// ... (Properties implements Map, you could just treat it like a Map)

See also:

Upvotes: 6

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