如何将 Scanner.in 值从一个方法返回到另一个方法

Question

我想制作一些简单的程序来计算产品的月费率。有两个输入：产品成本 - 100-10000 之间和费率数量 - 6-48 之间。我想像下面的代码那样做到这一点：import java.util.Scanner;public class Calculator {Scanner sc = new Scanner (System.in);double productCost;int numberOfRates;double loanInterestRate;double monthlyRate;Double print () {Calculator c = new Calculator();System.out.println ("Enter the value of your product from 100 to 10 000 : ");productCost=sc.nextDouble();if (productCost < 100){    System.out.println ("You have to choose price between 100 to 10000. Try again: ");    c.print();} else if (productCost >10000){    System.out.println ("You have to choose price between 100 to 10000. Try again: ");    c.print();} else if (productCost >= 100 || productCost <=10000){    c.print1();    return = productCost;   // how to return productCost to be used in next method print1()?}else return null;   }void print1(){Calculator c = new Calculator(); System.out.println ("Now enter how many rates do you want to pay from 6 to 48: ");numberOfRates=sc.nextInt();if (numberOfRates<6){    System.out.println ("You can't choose this number of rates. Choose between 6-48: ");    c.print1();} else if (numberOfRates>48){    System.out.println ("You can't choose this number of rates. Choose between 6-48: ");    c.print1();} else if (numberOfRates>=6 || numberOfRates<=12) {    loanInterestRate=1.025;    monthlyRate = (productCost*loanInterestRate)/numberOfRates;    System.out.printf("Your monthly rate is: "+ "%.2f%n",monthlyRate);} else if (numberOfRates>=13 || numberOfRates <=24 ) {    loanInterestRate=1.05;    monthlyRate = (productCost*loanInterestRate)/numberOfRates;    System.out.printf("Your monthly rate is: "+ "%.2f%n",monthlyRate);} else if (numberOfRates >=25|| numberOfRates<=48){    loanInterestRate=1.1;    monthlyRate = (productCost*loanInterestRate)/numberOfRates;    System.out.printf("Your monthly rate is: "+ "%.2f%n",monthlyRate);}}}问题是什么，我不知道如何从方法“print()”返回“双倍productCost”。ProductCost 是从输入中获取的，这是双倍的，但 NetBeans 向我表明它不是正确的类型。有人能帮我理解问题出在哪里吗？

Answer 1

简单地做

    return productCost;

return是关键字，而不是变量。它“返回”给定值并退出函数，以便调用该函数的实体可以执行以下操作：

public static void main(String[] args) {

    ...

    double cost = calc.print();  // note calc.print() PRODUCES a value, which we assign to `cost`

    ...

}

然后，您可以执行任何您想要的操作cost（或任何您选择的变量命名方式），包括将其传递给另一个函数。

Answer 2

您的程序需要在一些地方进行更改。我已经完成了这些更改并写在更新后的程序下面：

import java.util.Scanner;

class Calculator {

    Scanner sc = new Scanner(System.in);

    double productCost;

    int numberOfRates;

    double loanInterestRate;

    double monthlyRate;

    void print() {

        Calculator c = new Calculator();

        System.out.println("Enter the value of your product from 100 to 10 000 : ");

        productCost = sc.nextDouble();

        if (productCost < 100) {

            System.out.println("You have to choose price between 100 to 10000. Try again: ");

            c.print();

        } else if (productCost > 10000) {

            System.out.println("You have to choose price between 100 to 10000. Try again: ");

            c.print();

        } else if (productCost >= 100 || productCost <= 10000) {

            print1(productCost);            

        }

    }

    void print1(double productCost) {

        Calculator c = new Calculator();

        System.out.println("Now enter how many rates do you want to pay from 6 to 48: ");

        numberOfRates = sc.nextInt();

        if (numberOfRates < 6) {

            System.out.println("You can't choose this number of rates. Choose between 6-48: ");

            c.print1(productCost);

        } else if (numberOfRates > 48) {

            System.out.println("You can't choose this number of rates. Choose between 6-48: ");

            c.print1(productCost);

        } else if (numberOfRates >= 6 || numberOfRates <= 12) {

            loanInterestRate = 1.025;

            monthlyRate = (productCost * loanInterestRate) / numberOfRates;

            System.out.printf("Your monthly rate is: " + "%.2f%n", monthlyRate);

        } else if (numberOfRates >= 13 || numberOfRates <= 24) {

            loanInterestRate = 1.05;

            monthlyRate = (productCost * loanInterestRate) / numberOfRates;

            System.out.printf("Your monthly rate is: " + "%.2f%n", monthlyRate);

        } else if (numberOfRates >= 25 || numberOfRates <= 48) {

            loanInterestRate = 1.1;

            monthlyRate = (productCost * loanInterestRate) / numberOfRates;

            System.out.printf("Your monthly rate is: " + "%.2f%n", monthlyRate);

        }

    }

}

public class MonthlyRate {

    public static void main(String[] args) {

        Calculator calc = new Calculator();

        calc.print();

        // TODO code application logic here

    }

}

将您的程序与此更新的程序进行比较后，很容易理解这些变化。尽管如此，如果您需要任何进一步的帮助，请随时告诉我。