Java Arraylist，do while循环并调用方法

我需要创建一个数组列表来保存用户输入的电阻值。然后我需要询问用户使用哪种类型的方法来计算他的答案，然后返回答案。do while循环需要不断询问电阻值，直到用户输入数字0。计算必须从一级阻力中得出

***类***

import java.util.ArrayList;    

public class Resistance {

    /**
     * Holds an object type.
     */
    public int userChoice;

    ArrayList<Double> resistor = new ArrayList<Double>();

    /**
     *Chooses which process follows next.
     *@return circuitType
     */
    public final double calculateResistance() {
        if (userChoice == 1) {
            return calculateSeriesResistance();
        } else {
            return calculaParallelResistance();
        }
    }
    /**Returns object of parallel circuit.
     *
     * @return 1 / runningResistance.
     */

    public double calculaParallelResistance() {
        double runningResistance = 0;

        for (int index = 0; index < resistor.lenght; ++index) {
            runningResistance = runningResistance
                    + +1 / resistor.lenght;
        }
        return 1 / runningResistance;
        }

    /**Returns object of series circuit.
     *
     * @return runningResistance.
     */
    private double calculateSeriesResistance() {
        double runningResistance = 0;    
        for (int index = 0; index < resistor.length; ++index) {
            runningResistance = runningResistance + resistor[index];
    }    
        return runningResistance;
    }
}

import java.text.DecimalFormat;
import java.util.Scanner;

public class Main {
    /**
     * Makes a Constant.
     */
    public final static int DONE = 0;

    /**
     * Makes a Constant.
     */
    public static final int USER_CHOICE_SERIES = 1;

    /**
     * Makes a Constant.
     */
    public static final int USER_CHOICE_PARALLEL = 2;

    public static void main(final String[] args) {

        // TODO Auto-generated method stub
        DecimalFormat f = new DecimalFormat("##.00");
        Resistance myRes = new Resistance();
        Scanner keyboard = new Scanner(System.in);

        //Display Purpose
        System.out.println("\nThis program will calculate "
                + "the resistance of a Parallel or Series "
                + "Circuit\n");   

        //Display instructions
        System.out.println("Please enter the value of your "
                + "resistors separately, when done press 0 (zero)");
        int n = 0;
        do {
            System.out.println("Enter Resistor #" + ++n);
            myRes.resistor.add(keyboard.nextDouble());
        } while (myRes.resistor > 0);    

        // Ask Which Method To Use,
        do {
            System.out.println("\nEnter 1 to calculate "
                    + "a Series Circuit "
                    + "or 2 for a Parallel Circuit");
            myRes.userChoice = keyboard.nextInt();

            // Ask user again in case he enters something else
            } while (myRes.userChoice != USER_CHOICE_PARALLEL
                    && myRes.userChoice != USER_CHOICE_SERIES);

        //Output the total resistance
        System.out.printf("\nThe Total Resistance is "
                + f.format(myRes.calculateResistance()));
    }    
}

---

如前所述，您的代码几乎没有问题，让我们一步一步地将其分解

首先，ArrayList没有名为length的字段，您需要使用size（）来代替

其次，你计算并联电阻的方法是错误的。您并不是在电阻器上迭代，而是使用电阻器的数量来计算。正确的公式是：

1/Rtotal=1/R1+1/R1+1/R3+

将代码更改为：

 public double calculaParallelResistance() {
    double runningResistance = 0;

    //use size() instead of length, which doesn't exist in ArrayList
    for (int index = 0; index < resistor.size(); index++) {
        //also, iterate over each resistor's value, and to get it, 
        //use...err, get() method :)
        runningResistance +=  (1 / resistor.get(index));
    }
    return 1 / runningResistance;
}

---

那么，你有问题吗？那么。。这是我的密码。做你该做的，Stackoverflow？我在尝试创建Do while循环和停止它的sentinel值时遇到了问题。另外，整个过程是为arraylist添加输入，但不起作用。您的代码甚至无法编译。有很多问题，例如ArrayList没有长度字段…非常感谢Melquiades

private double calculateSeriesResistance() {
    double runningResistance = 0;
    for (int index = 0; index < resistor.size(); index++) {
        runningResistance += resistor.get(index);
    }
    return runningResistance;
}

//holds current resistor's value
Double val;

while(true) {
    System.out.println("Enter Resistor #" + ++n);
    val = keyboard.nextDouble();

    //only add if higher than 0
    if (val > 0.0) {
        myRes.resistor.add(val);
    }
    //0 entered, so finish the loop
    else break;
}