Question

我确定这是一个愚蠢的问题，但是我已经解决了很多。.我试图创建一个Java程序，根据用户输入的年数和金额来计算复利。但是我一直收到一个错误，认为void方法无法返回值。所以我将方法切换为double，因为多数民众赞成将返回什么，但是它告诉我double方法必须返回double。甚至在循环中返回双倍...请帮助

import java.text.DecimalFormat;

import java.util.Scanner;
public class Main {

public static void main(String[] args) {

        DecimalFormat df = new DecimalFormat("#.00");
            **strong text**
            Scanner reader = new Scanner(System.in); //creates scanner

            System.out.println("Enter number of years until retirement: "); //asks user to input number of years until retirement
            int Years = reader.nextInt();

            if (Years <= 0) {
                System.out.println("Please enter a valid number"); //if the number of years was invalid, exits the program and asks to enter a valid number
                System.exit(0);
            }


            System.out.println("Enter amount of money able to save annually: "); //asks user how much money they can input
            double MoneySaved = reader.nextInt();

            reader.close(); //closes scanner


            for(int i=0; i < Years; i++)
            {

                Total = MoneySaved * 1.05;

                return Total;



            }
            System.out.println("You will have $" + df.format(TotalAmount) + " saved up by retirement");



        }
    }

Answer 1

将方法修改为双并更改

def test_data_collection():
with mock.patch('moduleA.classA.send_over_socket') as mock_send_over_socket:
    A = classA()
    A.send_over_socket.return_value = 1
    with mock.patch('socket.socket') as mock_socket:
        mock_socket.return_value.recv.decode.return_value = "packet_string"
        with mock.patch('moduleA.ClassA.publish') as mock_publish:
            d = {}
            A.data_collection(d)
            A.publish.assert_called_with("0","500","2","1")

到

double MoneySaved = reader.nextInt();

我也看不到您对“总计”的声明；确保将其声明为double。

Answer 2

为此更改您的

    Double total = 0;
    for(int i=0; i < Years; i++) {
        total += MoneySaved;
        total *= 1.05;
    }
    System.out.println(total);

Answer 3

首先，主要的Java方法必须为void，并且void方法不能返回值（即使编译器也告诉您），尽管您可以使用return语句中断该方法的执行并返回到调用方法。

因此，要回答您的问题，您必须创建一个返回double的方法，然后将其打印在您的main方法中，或者不返回任何内容而只替换

return Total;

使用

System.out.println("You will have $" + df.format(Total) + " saved up by retirement");

PS：您似乎是Java的新手，所以一开始请阅读一些有关Java的内容，例如offical oracle tutorial

无效方法无法返回值-Java

3 个答案: