How can I create a get method to return a matrix reference?

I wrote:
public int[][] getTerrain(){
return this._mTerrain;
}

but how can I use the getTerrain() function in order to get values, I've tried:

int b=getTerrain()[i][j];

but it isn't working.

What does 'isn't working' mean?

kind regards,

Jos

It's ok I understood my mistake I didn't created the object to initiate the method of getTerrain()