在Java的ArrayList中查找特定的数组

Question

我正在尝试制作一个平均计算器，但使用实际的加权成绩上课。我做了一个数组列表，可以存储无限数量的双精度数，但是我不知道如何找到或使用它们。我对此并不陌生，我不希望有人为我做这件事，我希望他们解释一下并举例说明如何找到它并实现它。谢谢

代码如下：

import java.util.ArrayList;
import java.util.Scanner;
import javax.swing.*;

public class Averager{

static ArrayList <Double> array = new ArrayList <Double>();

public static void main (String[] args){


    Scanner input = new Scanner(System.in);

    double total = 0;
    int grades;
    int score;
    int counter = 0;
    double average;
    String type;

    type = JOptionPane.showInputDialog ("Which averager do you want to use, weighted or normal?");

    if (type.equalsIgnoreCase("Normal")){

        System.out.println ("How many scores do you want to average?");
        grades = input.nextInt();

        System.out.println ("What are your scores?");

        while (counter < grades){

            score = input.nextInt();
            total = total + score;
            counter++;
        }

        average = total / grades;
        average = Math.round (average * 100.0) /100.0;
        System.out.println ("The average is " + average);

    }else if (type.equalsIgnoreCase ("Weighted")){

        // this is the part where i need help
        System.out.println ("Enter the weights of the course, type 0 when finished");
        double weight = input.nextDouble();

        while (weight != 0){

            array.add(weight);
            weight = input.nextDouble();
        }

        for (double i : array){       //i was trying to follow a tutorial but this just outputs all of the variable where as i need section for specific ones 

            System.out.println (i);
        }

    }else{

        System.out.println ("Error 101, can't do that yet");
    }
}

}