title: Array of arrays/array of objects/arrayList of arrayList
body: <p>I'm doing a project, where I'm reading accelerometer sensor data from a smartwatch. The app that is made has a start and stop button, that starts and stops the sensor readings, respectively.</p>
  <p>I would like to start recording the data when the user presses start - I know how to access the sensor data, but I need a way to store the data until the stop button is pressed. Accelerometer data is X-, Y-, and Z-axis data, that could look something like this:</p>
  <pre><code>[2.034343, 8.342423, 0.012313]
  </code></pre>
  <p>So I need a way to store this type of vector within an additional array, in order to separate each vector recorded. Thus, the data structure I'm looking for should look something like this when having recorded three vectors of data:</p>
  <pre><code>[[2.034343, 8.342423, 0.012313], [6.031843, 2.349153, 0.012313], [1.734843, 5.342423, 1.012393]]
  </code></pre>
  <p>The data structure will be filled with these vectors in the time between the user pressing start to when stop is pressed.</p>
  <p>Do I need an ArrayList of ArrayLists? Or do you have any other suggestions as to what the best data structural solution to this is? As of right now, the data only needs to be stored as long as the app is running.</p>
  <p>I have no idea why I cannot figure out how to do this in Kotlin, I have only been able to make an ArrayList of ArrayList, however, instead of separating each vector with the brackets (as shown above) it just appends all the vector values to an array that holds all values (like a standard array).</p>
  <p>Hope I can get some help. Thanks in advance.</p>