arraylist在Java，将所有数据打印出来

Question

我现在正在学习Java，我正在尝试在我的项目中使用ArrayList，但它不起作用。请帮帮我。。。

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));

    }
}

我无法从单子上打印出任何东西。每次有人计算他的BMI时，它应该把他们放在一个arraylist中，当他们点击“继续”时，不。。。然后它应该会返回他们计算的所有体重指数。

Answer 1

尝试使用int变量的for循环

    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 2

您误用了列表结构的循环

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