double sum(double x){
	return x*(x+1)/2.0;
}

private void  computeButtonMouseClicked(java.awt.event.MouseEvent evt) {    
     int  answer=0;
     int  n=Convert.toInt(nField.getText());
           
     if(n<0){
     		loopLabel.setText("n must be  positive");
     }else{
     	for (int  i=1; i<=n; i++){
     		answer+=i;
     	} 
     	loopLabel.setText(""+answer);
     	methodLabel.setText(""+sum(n));
	}
}

 

Sample Code 5