java中的arraylist，将所有数据打印出来

Question

I am learning Java right now and I am trying to use ArrayList in my project, but it doesn't work. Help please...

public class TestCalculator {
    public static void main(String[]args){

        ArrayList<BMICalculator> bmilist = new ArrayList<>();
        //ArrayList<Double> bmilist = new ArrayList<Double>();
        do {
            double lengte = getLength("Geef de lengte in Meters:");
            double gewicht = getGewicht("Geef het gewicht in Kg:");
            BMICalculator bmi = new BMICalculator(lengte, gewicht);
            bmi.setBmi(bmi.calculateBMI());
            bmilist.add(bmi);

            for(double i = 0;i < bmilist.size(); i++){
                //System.out.println(i);
                JOptionPane.showMessageDialog(null, "List:" + i);

            }

            JOptionPane.showMessageDialog(null, "Bmi: " + String.format("%s", bmi.toString()));

        } while(getUserAnswer() == 'J');

    }

    public static double getLength(String message){
        String lengte = JOptionPane.showInputDialog(message);
        return  Double.parseDouble(lengte);
    }

    public static double getGewicht(String message){
        String gewicht = JOptionPane.showInputDialog(message);
        return  Double.parseDouble(gewicht);
    }


    public static char getUserAnswer(){
        String answer = JOptionPane.showInputDialog("Wil je opnieuw: j/n?");
        return Character.toUpperCase(answer.charAt(0));

    }
}

I cant get anything print out of that list. Every time someone calculates his BMI, it should put them in an Arraylist and when they click "continue", no... then it should return all the BMI's they calculated.

Answer 1

You misused a loop with a list structure

for (int i = 0; i < bmilist.size(); i++) {
     JOptionPane.showMessageDialog(null, "List:" + bmilist.get(i).getBmi());
}

Answer 2

Try the for loop with int variable

    do {
            double lengte = getLength("Geef de lengte in Meters:");
            double gewicht = getGewicht("Geef het gewicht in Kg:");
            BMICalculator bmi = new BMICalculator(lengte, gewicht);
            bmi.setBmi(bmi.calculateBMI());
            bmilist.add(bmi);
            // int variable instead of double inside for loop
            for(int i = 0;i < bmilist.size(); i++){
                JOptionPane.showMessageDialog(null, "List:" + bmilist.get(i));
    
            }
    
   }while(getUserAnswer() == 'J');

Answer 3

ArrayList<BMICalculator> bmilist = new ArrayList<>();
        do {
            double lengte = getLength("Geef de lengte in Meters:");
            double gewicht = getGewicht("Geef het gewicht in Kg:");
            BMICalculator bmi = new BMICalculator(lengte, gewicht);
            bmi.setBmi(bmi.calculateBMI());
            bmilist.add(bmi);
            JOptionPane.showMessageDialog(null, String.format("%s", bmi.toString()));
        } while(getUserAnswer() == 'J');

        System.out.println("Lengte    Gewicht   BMI");
        for(int i = 0;i < bmilist.size(); i++)
        {            System.out.printf("%-10s%-10s%s\n",bmilist.get(i).getLengte(),bmilist.get(i).getGewicht(),String.format("%.2f", bmilist.get(i).getBmi()));
        }
    }