public void actionPerformed(ActionEvent e){
    switch(e.getSource()){
        case radius:
            double r = validate(radius.getText());
            break;
        case height:
            double h = validate(height.getText());
            break;
        case out:
            out.setText(String.valueOf(h*r));
            break;
    }
}

public void actionPerformed(ActionEvent e){
    if (e.getSource() == radius) {
        double r = validate(radius.getText());
    else if (e.getSource() == height) {
        double h = validate(height.getText());
    else if (e.getSource() == out) {
        out.setText(String.valueOf(h*r));
    }
}

switch(e.getActionCommand()) {
    case: "Radius":
          ....
    case: "Height":
          ....
}