Question

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?

Answer 1

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:

• Java Tutorials – Essential Classes – Properties