RPNCalculator Code Confusion

Question

这是我的第二个编程类,我是Java新手.我一直在做我的第一个任务,它涉及类和方法.我对这些话题知之甚少,发现自己迷失了.我的任务要求我创建一个RPN计算器,询问用户两个数字和一个操作员.计算器对这两个数字执行操作,并要求再增加一个数字和一个运算符.然后,计算器使用第一组的结果,并使用刚输入的新数字执行另一个操作.当用户输入一个字母时,程序结束.我附上我的代码(原始).我需要尽可能多的帮助理解方法,就像编码一样.请尽快帮助,我想学习这个.任何帮助表示赞赏.

import java.util.Scanner;

public class RPNCalc 
{
    public static void main(String[]args)
    {
        Scanner keyboard = new Scanner(System.in);

        double v1, v2;
        String operator = keyboard.nextLine();
        char symbol = operator.charAt(0);

        System.out.print("Enter a value v1: ");
        v1 = keyboard.nextDouble();
        System.out.println();
        System.out.print("Enter a value v2: ");
        v2 = keyboard.nextDouble();
        System.out.println();
        System.out.print("Enter one of the valid operators +, -, *, /, nCr,:  ");
        operator = keyboard.nextLine();
        switch (symbol)
            {
             case'+':
                sum.writeOutput();
                break;
             case'-':
                minus.writeOutput();
                break;
             case'*':
                times.writeOutput();
                break;
             case'/':
                divide.writeOutput();
                break;
             case'q':
                System.out.println("Your last result was "  );
             default:
                System.out.println("You must choose an appropriate operator .");
             }
    }

    double value1, value2;
    int n;

    public static double sum(double value1,double value2)
    {
        double newSum = value1 + value2;
        return newSum;
    }
    public static double minus(double value1, double value2)
    {
        double newMinus = value1 - value2;
        return newMinus;
    }
    public static double times(double value1, double value2)
    {
        double newTimes = value1 * value2;
        return newTimes;
    }
    public static double divide(double value1, double value2)
    {
        double newDivide = value1 / value2;
        return newDivide;
    }
}

Answer 1

好的。开始了。我对你的程序做了一些修改。以下是修改程序时出现的问题。1. 任何类中都没有“writeOutput() 方法。因此我必须删除那段代码。2. 必须引入一个 while 循环来使其成为一个迭代过程。3. 向下移动operator.charAt( 0) 方法在我们读取操作符字符串之后。

由于您使用的是 switch 语句，因此无法将运算符值与“nCr”字符串值进行比较。要使用这个，您必须使用 equals() 方法进行字符串比较。

最后但并非最不重要的一点是，操作的结果应该是下一轮计算的输入之一。这意味着第一个操作的结果将被传递到下一个操作的第一个参数中。

import java.util.Scanner;

public class RPNCalc 
{
    public static void main(String[]args)
    {
        Scanner keyboard = new Scanner(System.in);

        double v1, v2;
//        String operator = keyboard.nextLine();
//        char symbol = operator.charAt(0);
        char operator = ' ';//First time around, set this to an something other than 'q'
        String operatorString = " ";
        System.out.print("Enter a value v1: ");
        v1 = keyboard.nextDouble();
        System.out.println();
        while(operator != 'q')
        {
            System.out.print("Enter a value v2: ");
            v2 = keyboard.nextDouble();
            System.out.println();
            System.out.print("Enter one of the valid operators +, -, *, /, nCr,:  ");
            operatorString = keyboard.next();//nextLine() doesn't wait until the user hit enter
            operator = operatorString.charAt(0);
            switch (operator)
            {
             case'+':
                v1 = sum(v1, v2);
                System.out.println(v1);
                break;
             case'-':
                v1 = minus(v1, v2);
                System.out.println(v1);
                break;
             case'*':
                v1 = times(v1, v2);
                System.out.println(v1);
                break;
             case'/':
                v1 = divide(v1, v2);
                System.out.println(v1);
                break;
             case'q':
                System.out.println("Your last result was "  );                
             default:
                System.out.println("You must choose an appropriate operator .");
             }
        }
    }

    double value1, value2;
    int n;

    public static double sum(double value1,double value2)
    {
        double newSum = value1 + value2;
        return newSum;
    }
    public static double minus(double value1, double value2)
    {
        double newMinus = value1 - value2;
        return newMinus;
    }
    public static double times(double value1, double value2)
    {
        double newTimes = value1 * value2;
        return newTimes;
    }

    public static double divide(double value1, double value2)
    {
        if (value2 == 0)
        {
            System.out.println("Division by Zero. Try again");
            return value1;
        }
        double newDivide = value1 / value2;
        return newDivide;
    }
}