Subtraction of dissimilar doubles resulting in 0.0

I'm trying to subtract two small doubles, both of which I got using the system time:

start = System.currentTimeMillis();
end = System.currentTimeMillis();

      

        
        
        
      

    

Then I subtracted two ( end - start

) and tried to store that value into an array double[] data

, which I did. For some reason, the result of this, instead of being double, continues to output 0.0

.

I have initialized the data array like this:

private double[] data = new double[maxTaps+1];

      

        
        
        
      

    

where MaxTaps

is some constant

I am using a textView to display the values ​​that I am walking through. For some reason, when I just print ( end - start

) it will give me a double that is nonzero. But if I put this double ( end - start

) in my data array and try to print a double from the data array, it results in 0.0.

For example: I am trying to get the time from the moment the button changes color to the moment it is used. After changing the color of the button, I set the start time. Then, when the user removes a specific button, the end time is recorded using the method described above and the two are subtracted and added to my dataset. The weird part looks like this: when I output data like below, the result is always 0.0

bottomText.setText("Data point " + Integer.toString(taps) + ": " + String.valueOf(data[taps]));

      

        
        
        
      

    

but if i change data[taps]

to ( end - start

) (shown below) then i get a reasonable value

bottomText.setText("Data point " + Integer.toString(taps) + ": " + String.valueOf((end - start));

      

        
        
        
      

    

I am really lost here because they must be the same.

Also, I just include what one of my click listeners looks like a button, which might also be helpful

buttonTopLeft.setOnClickListener(new View.OnClickListener() {
         @Override
         public void onClick(View view){
            if (lit == 1) {
                end = System.currentTimeMillis();
                data[taps] = (end - start);
                taps++;
                buttonTopLeft.setBackgroundColor(Color.WHITE);

                mHandler.postDelayed(new Runnable() {
                    public void run(){
                        doUpdate();
                    }
                }, 1000);
            }
         }
    });