title: Result of String.Format() is ignored but why?
body: <p>So I wanted to round my double values into numbers that contain only 2 decimals but cant figure out how to do it. How can I change my code in order to get 2 values that are rounded for 2 decimals? Any help with this would be appreciated.</p>
  
  <pre><code>btnAdd.setOnClickListener(new View.OnClickListener() {
  
      public void onClick(View v) {
          num1 = Double.parseDouble(numBase.getText().toString());
          num2 = Double.parseDouble(numNikotin.getText().toString());
          sum = num1 / 20 * num2;
          String resultN = Double.toString(sum);
          String.format("%.2f", resultN);
          addResult.setText(resultN);
          sum = num1 - sum;
          String resultB = Double.toString(sum);
          String.format("%.2f", resultB);
          addResult2.setText(resultB);
      }
  });
  </code></pre>