I'm new to android development, I trying to create a simply Pythagorean Calculator, I need help with reading if a lines blank, but still calculates instead of failing.

Here is my code

```
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.text.TextUtils;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

private EditText sideAObj;
private EditText sideBObj;
private EditText sideCObj;
private EditText outputObj;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    sideAObj = (EditText) findViewById(R.id.SideAInput);
    sideBObj = (EditText) findViewById(R.id.SideBInput);
    sideCObj = (EditText) findViewById(R.id.SideCInput);
    outputObj = (EditText) findViewById(R.id.OutputText);
}
public  void calculateClick(View v){
    try {
        double sideA = Double.parseDouble(sideAObj.getText().toString());
        double sideB = Double.parseDouble(sideBObj.getText().toString());
        double sideC = Double.parseDouble(sideCObj.getText().toString());

        if (sideAObj.getText().toString().equalsIgnoreCase("0")) {
            double pt = Math.sqrt((sideC * sideC) - (sideB * sideB));
            outputObj.setText(String.format("%.2f", pt));
        }

    }
    catch (NumberFormatException ex){
        Toast errMess = Toast.makeText(getApplicationContext(),"Enter Numbers Only",Toast.LENGTH_SHORT);
        errMess.show();
        outputObj.setText(String.format("%2.f",0.00));
        return;
    }

}
public  void clearClick(View v){
    sideAObj.setText("");
    sideBObj.setText("");
    sideCObj.setText("");
    outputObj.setText("");
    sideAObj.requestFocus();

}

```

}
My program will calculate if their is a Zero on 1 line, but if I leave it blank the program fails entirely, whats the best way to prevent that.