How create a battery level array?

Question

I need to create a battery level array to insert it in a graph like

values.add( batterylevel )

How can i create this array? I mean, i know how create an array but i don't know how create one for the battery level. How can i do it? This is a way to have the battery level

public float getBatteryLevel() {
    Intent batteryIntent = registerReceiver(null, new IntentFilter(Intent.ACTION_BATTERY_CHANGED));
    int level = batteryIntent.getIntExtra(BatteryManager.EXTRA_LEVEL, -1);
    int scale = batteryIntent.getIntExtra(BatteryManager.EXTRA_SCALE, -1);

    // Error checking that probably isn't needed but I added just in case.
    if(level == -1 || scale == -1) {
        return 50.0f;
    }

    return ((float)level / (float)scale) * 100.0f; 
}

I need have double value to intert it in the chart.