Isn't saveStrings() about saving a String[] into a file?
I don't see the need to store away something from RAM into a file system! 
Unless you wanna transfer it to another program or recovered from another run.

I believe you're trying to make a tiled-based graphics game, am I right?

If it is so, each coordinate myMap[x, y] would contain a value representing a type of tile.
Be it a wall, an object or an enemy!

Let's say wd & hg are the dimensions chosen by the user. Then we got:
myMap = new byte[wd][hg];

Now you just need to make up a value for each tile type:
final static byte tileWall  = -1;
final static byte tileRoad = 0;
final static byte tileWater = 1;
final static byte tileTree = 2;

and so on...!  

And apply those for each 2D coordinate from myMap[][]. 

What is easier way (IMHO), is to use serializable.

Two ways:
- Build an array of strings from your array of data, using str'() for example. They use saveStrings() as you planned to do.
- Just save the binary data from your array, using saveBytes(), for example.

Having a small bit of code might help to give more precise advices...

Perhaps createOutput() is what you need, but it is not easy to use.

To use saveStrings(), you have to convert your data to string format, you can take the opportunity to put it all in a 1D array.
Take a look how pixels[] is a flat version of a 2D matrix of colors.

Alternatively, you can indeed put all your 2D binary data in a single 1D array, using arrayCopy().

I don't understand why you need to save your 2D maps from Processing. (Unless it's random generated?)
You should create them outside using a simple text editor!

Once you have your (100?) maps, you can load them into your game.
Either all at once, storing them in 3D arrays, or a specific 1 loading
whenever the player changes current map to next 1!

To save memory, I advise you to use datatype byte instead of int for the arrays,
since an int is 4x bigger than a single byte!

As I've mentioned before, you should arbitrarily determine some values/characters
to represent blocks/objects of your world within a map!

Some examples once more:

final static byte tileEmpty = ' ';
final static byte tileWall = '#';
final static byte tileEnemy = 'e';
final static byte tileTree = 't';
final static byte tileRiver = 'r';
final static byte tileBoulder = 'b';

and so on... Just make the ones you need for your game world!